caster helps your wheels return to straight after turning.
caster adds camber the more you turn your wheels. (think like a grader or mercedes or beemer) next time you see one parking, check the camber angle when they're on full lock.
experiment to find the best settings for your own requirements, but a reputable track related suspension shop should be able to give you some good ideas.
alternatively google the subject as there is pages and pages of info out there.
-dave