Ditto what flexi said. I try to have serveral options as to where I will set up for each area and let the prevailing wind dictate which one. Like wmi said I will go out of my way to not let scent drift into what I believe is a core area of a buck I am hunting.
With that said, some times there is just no choice bust to bust on through like Bruce said, if you jump deer it's not the end of the world. I have busted deer out from under my tree going in just to have deer(maybe the same deer) come back under me 15 minutes after get in the tree.
I said it before and I'll say it again I believe the most important thing about scent is to not leave it on the ground, grass or limbs you contact as you walk in.