I've probably done a few thousand alignments so I'll add a few things here.
First off I have never aligned anything specifically for auto-x, nor do I know how aligning stuff out of spec on purpose will do at the limits of traction, I'll let the people who actually race do that.
I do know exactly what each change will do in general when it comes to daily driving.
I used to be into Jeeps and whatnot... I made this write-up specifically for aligning solid axle vehicles... BUT I go over the basics of camber/caster/toe/thrust angle/scrub radius/etc etc... which is worth a read.
http://www.jeepforum.com/forum/f9/end-all-all-tj-alignment-thread-long-read-663777/
A few clarifications on some stuff I saw that was wrong or unclear while I was browsing some of this thread:
Thrust angle will not cause a pull... it will not cause any unusual tire wear assuming all else is in spec. It is basically the angle that the rear "axle" is pointing(average of the rear toe). If your thrust angle is off by much, your car will "crab walk" town the road sideways. I'm sure when it comes to racing you will probably notice if it's more than a couple tenths of a degree off when comparing left vs right turns, but on the road, you will never notice even 0.50 deg thrust angle. Most leaf sprung vehicles have a tolerance of 1, some even TWO full degrees of thrust angle.
In reality you can have SO much s*** wrong alignment wise and still have it drive straight down the road... case in point is my Jeep. It's on 40" tires and I have the front axle INTENTIONALLY 3" to the passenger side for driveshaft clearance. It's not noticable unless you really look at it for a few minutes... but it drives straight and I've put 3000 miles on the tires with no unusual wear. It crab walks down the road a little bit, but the streering wheel is straight, and I've had it 70mph no problems.
All that thrust angle is is this: It is the angle at which your rear wheels are pushing in relation to the front axle... YOUR FRONT AXLE MEASUREMENTS RELY SOLELY ON WHAT THE ANGLE OF THE REAR IS when it is on an alignment machine... Lets make an "example":
Start with these specs in this car with wheel straight and all that(we're only looking at toe because that is the only thing that affects thrust angle):
0.05 LF toe, 0.05 RF toe
0.05 LR toe, 0.05 RR toe
That car has a thrust angle of 0... it's all straight.
Now lets change the rear toe to affect it... If you were to set the rear toe to 0.00 LR and 0.10 RR, this will give you a thrust angle of 0.05 to the left. The machine will usually display this as "-0.05" FWIW.
BUT since the front is based off the rear... by changing the rear, that changes the front measurement according to the machine... it will now display:
0.10 LF toe, 0.00 RF toe
0.00 LR toe, 0.10 RR toe with a thrust angle of -0.05 which we already went over.
Your total toe in both front and rear has not changes... you have just changed the direction of what is called "center."
So now your steering wheel will be slightly off center, and the car will slightly crab walk down the road(though honestly you probably wouldn't notice it, even following behind because of how little it is).
While we're talking about toe... if the wheel is straight, and your total toe is correct, it does not matter what your individual toe is(on the front axle)... because as soon as you start driving they will fight each other and center themselves to be equal on both sides.
Camber: If your camber is off from left vs right, your car will pull to the side with more POSITIVE camber. Pictures and more explanation is in the link I posted. As far as the pull goes, in my experience... it is usually only noticable at low speeds... maybe 25mph or so. Also see the next section about why a FWD car will not pull anyways... at least not enough to really notice.
Caster: This is what affects your "return to center" and having it off from left vs right will usually make turning one way vs the other a little bit easier than the other. Most RWD cars and some FWD cars are set up to have intentionally have more positive caster on the passenger side... this is to combat road crown. This is so your car won't wander to the right side on the highway when you're taking a 600 mile trip. Note that in FWD cars... caster does DAMN NEAR NOTHING to affect the pull of the car. If your car is physically pulling on the highway... it is very likely your tires more than anything. Rotate them... one of them has more rolling resistance than the other. I have seen a full 1.5 degree difference in L vs R caster in a FWD car and it still drove straight. RWD cars are far more susceptible to caster pull.
Toe: Everyone pretty much got this right on. You want it as close to zero as possible... toe in = stability, toe out= twitchy feeling... but I'll let the road racers/seasoned auto-xers go more into that. Basically keep it in spec if you don't want to burn through tires all the time. Most factory vehicles have 0.20 degrees TOTAL toe at the most as spec(that's left + right)... it's pretty unusual to have more than that... though more common would be 0.10 degrees total(0.05 one each side).
Maybe once I have a season of auto-x under my belt I'll feel inclined to make a write-up specifically for our Mazdas.
At the dealer I work at, for a while I was doing 10-12 alignments per day on cars that were to be sold and had a problem on a test drive... 5/10 "pulls" are from tires... 4/10 "pulls" are actually people thinking the steering wheel being off center means it's pulling... the last 1/10 was a legitimate pull from an alignment... and it was always a RWD car or RWD biased AWD SUV.
