Whenever I get setup in my treestand, I always play over in my mind what I will do if a deer comes in from any direction. I also know exactly what I will do if I have to turn to shoot. Of course, that depends on a number of varaibles...how close is the deer, is he acting calm, can I make my move once he's goes behind cover?
The point is I really try to anticipate what I will do no matter which direction that deer comes from.