I usually jack under the front suspension. You need a fairly low jack though. Otherwise, under the crossmember below the engine is a good place (put a block of wood between your jack and the cross member to spread the load), since you thus jack up both sides at once and you leave the suspension area free for your jack stands - which you do use every time of course, don't you?
At the back I usually just place a block of wood under the diff and jack it up there. This does mean that you start out by moving the suspension up in stead of the body, but if you just lift enough it's not a real problem.