See this article (especially the latter part: Controlling your Memory Manager) for tips.

http://developer.java.sun.com/developer/TechTips/2000/tt1222.html

Incremental GC usually gives you shorter GC pauses. Also you should usually increase the nursery size which by default is rather small (nursery tip courtesy of Peter Tillemans and Francois at one of the J2EE intro trainings.)