There are ten things (off the top of my head in no particular order) that most effect the handling of your vehicle.  They are:

1.) Weight of the vehicle and distribution of that weight.
2.) Engine placement/motor mount stiffness
3.) Frame stiffness, and where the frame is stiffest (front/rear).
4.) Spring rates.
5.) Shock stiffness and ability to dampen the movement of the springs.
6.) Center of gravity of the car, effected by height/length/track width/motor placement/suspension setup
7.) Wheel base and track width.
8.) Tire width, sidewall height/stiffness, tread compound and wheel size.
9.) Alignment, front and rear.  This includes camber, positive or negative, and toe in/out.
10.) Suspension design/geometry and swaybars

I'll tackle these in order as much as possible.  But first, definitions of a few terms.

Oversteer:  Oversteer is a term referring to the tendency of the rear wheels of the car to "rotate" or "come out" in a corner.  A car that likes to oversteer is often referred to as "tail happy".  RWD cars, and especially rear engine RWD cars, are famous for this.

Lift Throttle Oversteer: Same as the above, but only happens when you let off the gas.  Usually an issue with RWD cars, especially rear engine RWD cars.

Understeer:  The tendency of the front of a car to "push" or "plow".  Basically understeer is when the car won't turn in, due to either inadequate traction, bad alignment, or excessive speed.  If you're going 100mph and try to take a 90 degree corner, and the car slides straight, then your car is understeering.

Four Wheel Drift:  When a car, in a corner, slides all 4 tires equally or nearly so, essentially "drifting" on all 4 tires.

Bumpsteer:  Slight changes in the cars direction as a result of the rebound from hitting a bump at high speed.

Camber: The vertical position of the wheels in the wheel wells in relation to the body.  "Negative camber" means the "top" of the tire is tilted in more toward the body, and the contact patch further away from the body.  Negative camber looks like this, if you're looking at the car from the front:  /-----\
Positive camber looks like this: \-----/
Keep in mind that these are rather extreme examples.  Camber is usually measured in degrees.

Toe: Toe is the relation of the wheel to the body, from front to back, referenced to as toe "in" or "out".  If looking down on the car from the top of the car, toe in would look like this:  /-----\
and toe out would look like this: \-----/
Again these are extreme examples.  This much toe and your tires would be smoking as you drove down the road.  Toe is usually measured in fractions of an inch, though occasionally it is measured in degrees.

Swaybars/Anti-roll bars: Bars that work with the suspension to reduce body roll

Damping: The ability of a shock/strut to slow and control the oscillation of the springs as they move to absorb road irregularities.

Jounce damping: The ability of a strut/shock to damp compression movements of the suspension.

Rebound damping: The ability of a strut/shock to damp the release of the energy stored in the springs after they've absorbed a bump.

Fundamental Concepts

1.) Weight of the Vehicle

2.) Engine Placement and Motor Mount Stiffness

3.)  Frame Stiffness

4.) Springs

5.) Shocks and Struts

6.) Center of Gravity, Ride Height, and Top Heaviness

7.) Wheel Base and Track Width

8.) Wheel Width, Tire Width, Sidewall Height/Stiffness and Tread Compounds

• Speed Rating
• Heat/Temperature rating
• Traction Rating

9.) Alignment

That said, let's continue.  Why is the factory alignment in most cars so horrible?  First, let's understand the technical reason of why it is so bad for handling.  The major problem is camber.  Car frames and suspension flex.  In a corner, even a mild one, the wheels will tend to "fold under" on the side of the car facing the outside of the corner due to the side-load being placed on the suspension.  If you have positive camber you have less traction to begin with, since the tire patch is already lessened by the slant inward of the tire, leaving part of the tire off the ground or with less forceful contact.  You go into a corner, the wheels fold under more.  For example (hypothetically) if a car has +.2 degrees of camber in the front going into the corner, depending on the frame stiffness, it might be pushed more positive to the point you might have +.8 degrees or more of positive camber.  This decreases the actual amount of tire contact patch even further.  You end up taking the corner on the outer edge of the tire, not on the tread.  The faster you go or the weaker the frame and/or suspension components, the more they push under, and the less traction the tire has on the pavement. 

The rear tires, having more negative camber, tend to grip more while in a corner.  Why?  Again, the force on the contact patch of the tire is pushing the wheels positive in camber again.  -1 degrees negative camber is the factory limit on most of the 2.2/2.5L turbo FWD Mopars for the rear wheels.  In hard cornering, they fold under, and more rather than less tire patch is in contact with the road.  This makes the rear stick and the front slide, causing the dreaded understeer effect.  With the alignment as bad as the factory ones tend to be, you get a lot of tire squealing and screeching as a warning before the car starts losing a significant amount of grip.  Plus, this bad alignment lowers the ability of the car to take corners quickly.  So instead of 16 year old Johnny taking a corner too fast and nailing the median at 80mph when the tires break loose, the car is handling so bad he's only pushing it at 40mph when he hits.  This has an obvious effect on survivability of accidents when people screw up.

Also, people don't know how to handle oversteer.  Take your average, stereotypical minivan driving Mom.  She's in a rush to pick up Susie from ballet practice since she was busy watching Jerry Springer and lost track of time, so she takes a corner fast to beat a yellow light.  If the car is set up to have the tires scream loudly long before there is any terminal danger, she'll take corners slower for fear of sliding nose-first into something.

Now, set up that minivan's alignment to have a bit of oversteer and grip better.  She's taking the corners 15mph faster, and whoops, the tail end steps out on her.  What does she do?  Panics and nails the brakes!  Sccrrreeeeccch, BANG!  360's across the intersection, wraps her minivan around a light pole, leaving her kids to walk home in the dark.  Does she accept it as her fault?  Hell no!  The minivan did it, not her.  "I was just taking the corner and the car just spun all of a sudden!" she'll sob to her lawyers, and next thing you know, Ma Mopar is in for a 10 million dollar lawsuit and is on 60 minutes for having "uncontrollable cars"! 

Think it wouldn't happen?  The State of California sued Porsche for it's 1980 911 Turbo, because people complained so much that it was "uncontrollable" since they didn't know how to deal with lift throttle oversteer that most rear drive, rear engine cars tend to have. SUVs, Trucks, and Vans tend to use bad alignments a lot as well.  Otherwise, these top heavy vehicles would have a greater tendancy to roll over in the corners instead of sliding.

So, you're not the average driver, I'm hoping, if you're here.  Are you ready to step outside the factory limits and improve the alignment of your car?  OK then.  First of all, chuck the factory alignment.  If you're going to do a bunch of modifications to the cars suspension, do that before you get the alignment, for obvious reasons.  Every modification to the car changes how it handles a bit, making it more or less controllable, making it understeer or oversteer more, and decreases or increases body roll.  If you align it first then add bigger sway bars, urethane bushings, etc., you'll likely be less happy with how it handles.  Changing a car from the factory suspension requires balance.  The alignment is the final touch to a well set up car, meant to balance it to perfection.  How you want a car to handle depends on your driving style.  I prefer a tad bit of oversteer in hard cornering, leaning toward neutral.  If you autocross a lot, you might want a lot of oversteer.  If you're uncertain of your reflexes, or don't know how to counter oversteer, you'll want a neutral to slightly understeering car.  A lot of people are most comfortable with a car set up for a bit of understeer or four wheel drift tendencies, since that's what they're used to.  If you give up your oversteer, the car loses it's ability to a degree to take tight corners quickly.  If you don't know how to control oversteer, you'll lose it and spin out.  If you do a bit of understeer, in high speeds the car will push, and you'll lose a bit of control (if you're lucky) to all of your control if you really screw up, then slide into a guardrail or worse.  This is why I like a bit of oversteer, if nothing else, you can countersteer out of it if you're quick and precise and don't panic.  I don't claim to be fantastic at it, I'm perhaps an average driver, but that's how I like the car to handle.  For this reason, I'll give a few general good alignment tips.  What you pick depends on you, your car, your driving style, and of course, tire wear.  I'd always plan for a car that oversteers some at 0 camber on all 4 wheels.  This gives you room to play with, it's a lot easier to get a car to understeer with alignment changes than oversteer.  In my experience it's pretty easy to achieve this in a FWD Mopar if you know what to do.

Any 2.2/2.5L Turbo Mopar should have adjustable front camber.  With most Neons and many other cars, the camber may or may no be "frozen".  If you're stuck with this, you can do a couple different things.  On my Neon I've used "Crash bolts" (Mopar P/N 4762135 for the fronts, I'd not touch the rears since it's so hard to get them even).  These are little more than slightly skinnier bolts than stock, which gives you some play in the holes to allow about 1 degree positive or negative camber.  I did this on my Neon with good success, though I'd like a bit more to counter the stock -1 degrees of camber.  This isn't good for if you like hitting curbs though, since they have a slightly higher tendancy to "slip" than stock bolts under impacts.  Autocrossers put some paint on the strut before tightening the bolt down to "glue" it down and give it more hold.  This is also handy since it shows you if it's slipped.  Another method is using a die grinder to grind the hole in the strut into a slot.  Or, better yet, get Konis which come with adjustable camber (unless they're OEM ACR struts, which are black-painted Konis without the adjustable camber).  Or you can go all-out and get camber plates, which allow the greatest range of available settings.  If you do get camber plates on a Neon, don't bother with the rears unless you like cutting sheet metal.  Most of the aftermarket ones require modification in the rear to make them fit, and the -1 in the rear is a good amount for most handling setups short of an all-out race car.  If you're going for camber plates, though, you might as well go with a full coilover suspension for a Neon in my opinion, since you'll have more adjustability that way.

Most older Mopar turbo cars have a solid rear axle and use shims behind the spindles to adjust the camber/toe.  Alignment guys hate these, so be forewarned, and make sure they understand exactly what you want so they don't have to do it twice.  Usually they don't complain about negative in the rear since up to -1 is in spec for our cars generally.  Make sure they're accurate though, one guy I took my car to had one at -.6 and the other at -1, and said, "Well, it's in spec!" even though the car pulled right.  The Neon uses adjusters built into the rear control arms which are easier to adjust than taking the whole brake assembly off like on the turbo cars. 

First, my favorite, neutral with a bit of oversteer.  For this, you need a car that has a bit of a tendency to oversteer already by following the tips above.  It's simple, really.  If you corner hard a lot, like I do, you'll want some greater than average amount of negative camber.  If you drive more mildly, and are worried about wearing the inside of the tire, go for less, say 30-40% less on all 4 wheels for this particular type of alignment.  On my '85 Laser, even with only a few mods, this worked well:

Front: -1.4 degrees, 1/16" toe in (you can go 1/16" toe out, but you'll hurt straight line stability)
Rear: -1 degree, zero toe

A more "mild" alignment, in this case, might be -.9 in front with -.5 in the rear.

Note: I can only vouch for the alignment specs I've tried on my car, the rest I'm "guesstimating".  Again, use your judgment for your own car!

Next, the "Extreme oversteer" solution.  Use this only if you autocross or drive lots of tight, sharp twisties a lot and _know_ how to manage that ass end coming out!

Front: As much as you can get (-1.6 is as much as you can get out of Konis/Eibachs from what I've seen), 0 toe
Rear: -.5 or approximately 65% less than the fronts.  If you really like oversteer, go for 0 in the back.  I know some autocross guys actually remove their front sway bars to get more oversteer.  Adjustable shocks, mentioned above, really come in handy for tuning this kind of thing.  -1.5 in front should be plenty for street driving, I've found -1.4 to be about perfect for balancing tire wear and handling on my car.  -1.6 wore the inside of the tire a bit.

Then we have the "4 wheel drift" solution.  This one will likely take an alignment or two of fine tuning to get exactly right for your car:

Front: -1.1 , 1/16" toe in
Rear: -1, zero toe.

For "Slight Understeer".  Again, fine tune:

Front: -.7, 1/16" toe out
Rear: -1, zero toe.

I'm pretty sure no one wants extreme understeer.  At this point, I'm sure you can guess the logic of picking alignment specs.  More rear negative camber than the front, more understeer.  Less negative camber in the back, the more it will oversteer.  Having the same camber on all 4 wheels generally doesn't work, the frame stiffness isn't the same front to back, plus most FWD front engine cars have more weight in the front than the rear.  Thus it takes more to make the front end "stick".  If you want a less extreme amount of camber, you can go for less, as long as you do it _equally_ all the way around the car.  Just don't go positive if you can avoid it!  Even -.8 on my Laser in the front resulted in tire wear on the outside of the tire more than the inside, and corner harder than most people as well.  On my Neon, -1 was a bit too much for winter driving on my Blizzack tires, and there was slightly more wear on the inside than the outside.  In an ideal world you could tailor your alignment to the seasons, but oh well.
 
By following these general guidelines, you can set up your car to handle the way you want it to, even if it means a few trips to the alignment shop and some stubborn behavior on your part when it comes to dealing with the alignment techs.

10.) Suspension Design, Geometry, and Swaybars

These are the rear end links for my Suspension Techniques swaybars I have on my Neon.  The stock links if you have a stock bar are quite different, being just a piece of metal that looks like a barbell with bushings on each end.  On these end links, the heim joint bolts to the spindle on the rear wheel, and the side with the red bushings mounts over the bar.  This is a better design since it uses a heim joint in place of the lower bushing, making the bar less likely to "bind".  Binding is when the swaybar gets "Stuck" in the suspension, not allowing the wheels to move any further.  This makes the spring rate essentially infinite, making the rear suspension act like it's bottoming out.  This unsettles the rear end, usually causing sudden snap oversteer or understeer depending on which bar binds.  Here you can see the end links installed on the rear bar:

As you can see, the bar bolts in to the bushings on top, then it mounts to the body as well in the middle of the bar.  The front end is similar.  The middle of the bar bolts to the body with bushings, like this:

That is the rear frame rail of a Neon.  It has integrated slots to mount the bar to.  The bar stretches off to the wheel above, then below it runs to the opposite frame rail, then to the opposite wheel.  To help things make more sense, here's a picure of how a typical front swaybar is installed:

As you can see, it bolts to the body in the middle, then to each control arm on either side of the car.  The Daytona, Omni, Spirit, etc. use similar designs on the front, except they don't use end links, they have hard urethane bushings that slide over the bar which then bolts on to the bottom of the control arm.  This works but makes the bar more likely to bind, reducing the independence and wheel travel of the front suspension.  Polybushings.com sells end-link style replacement bars for this reason.

You usually want a smaller rear bar than front bar, again following the rule that whatever end of the car you make stiffer will yield either understeer or oversteer.  A larger rear bar with a small front bar will result in a ton of oversteer, and vice versa will result in a tendancy to oversteer.  Some autocrossers disconnect the front bar for this reason; they like the extra oversteer for the tight corners that autocross often has.  The same goes for the type of bushings used with the swaybar.  Urethane bushings up front and rubber in the rear will increase the car's tendancy to understeer; the opposite will result in more oversteer.

Swaybars aren't the end all solution to roll stiffness however; they're meant more for "tuning" the suspension.  The springs are where you should focus first, then fine tune it with swaybars.  A car with 600lb/in rear springs and 200lb/in front springs will have much more tendancy to oversteer than a car with a 18mm rear bar and no front bar.  You want to get the car close to what you want with springs and shocks/struts, then fiddle with swaybars and alignment settings from there.  Of course if you have no rear bar (especially on a Neon) I'd recommend it even with the stock setup.  The car will turn in much better, understeer less, and generally be more fun to drive.  On the cars with the solid rear axle you might try welding a plate of 1/4" steel to the rear axle over the "U" where the stiffener bar is welded.  It seems to help a bit, especially on cars with the weaker rear axles.  I'd recommend trying one of the aftermarket swaybars however, as they'll reduce body roll and also help keep the rear axle located.  They also don't require a lot of grinding and cursing and scaring the neighbors with bright eerie blue glow flashes coming from your garage at 2am while you weld the plate on, and will weigh less too.

Conclusion

I've covered a lot of material here, and there's still more out there.  I've tried to pull personal experience and research into one guide that will prepare you for the trials of getting your suspension set up the way you want it, and I hope I've succeeded.  Again, if anyone has any comments, corrections, or things I've missed, please e-mail me, I'd be happy to speak with you.