these are the two ways you can get corrected steering, the top one is WAY easier, but the other one has its uses, so its included as well.
the point of force part is where you control arm or spindle mount frame side should be, forward of the center line of the wheel.
the red line is the center of the wheel
the blue line is the angle of the spindle
these pictures both assume you are (from the front) looking at the left or "passenger" side of the vehicle, you adjust as needed for the other side.
a real world example of this is spinning casters, they use a more extreme angle to get the same result. check them out if you need some hard evidence it works.
also, a good book to get if you are really getting into this, Chassis Engineering, by herb adams has alot of info(oh yeah and retail is under $20). there are also other books, but I own this one and its been very helpful to me. make sure you check on Amazon or something similar for a review of a book before you waste time paying for it. there are some VERY helpful reviews about most tech books on amazon.
I looked at the wikipedia from the other post, that caster adjustment to the rear is used to correct steering misalignment on suspension. it is a little different, same theoary, but its reversed to get a different effect. the important thing to remember is you want to get the axle center BEHIND the point where force is applied, this will ALWAYS result in self correcting steering