A few things that really helped me out are learning to sit still, I sit for hours with minimum movement. When I turn my head it is in slow motion or with the breeze (when the leaves rustle). Learning to sit still and patience. Deer hear really well, see movement and not shape so well. Really not much you can do about your scent except try to position yourself to minimize the impact.
I hang a feather near where I'm sitting and look into the breeze much more than with the breeze. If you hear a noise or see movement don't jerk your head around, move slowly.
If the Deer spook all isn't lost, I'd say about fifty percent of the time they return after 3/4 of an hour. It depends on how spooked they are.
Where the forest or the thickets meet the open areas are the best place to hunt IMO. Deer are going to be nervous moving into the open, so it is even more important to stay still.
Head down feeding is the best time to shoot. I've let more Deer pass by than I've shot. I pick my shots and almost never snap shoot. I've spooked Deer with the click of a safety or the sound of two open zipper halves brushing together. It is the unnatural sounds that spook them.

Good luck.