Make your practice as realistic as possible. Shoot the gun and load you will be shooting hunting, at the range you anticipate your hunting shots will be, in the conditions you anticipate...wind, cold, snow, heat whatever. Shoot in the positions, off your day pack, off hand etc. Alot of times you have to shoot when you just climbed a hill and may be out of breath. To simulate this I run to whatever range I'm shooting at (200 yards, 300 yards etc) when I check my targets so that my heart rate is up when I get back and then I shoot to simulate maybe having to shoot during a steep rigdge climb.

This is assuming of course you have the basics of breathing control and trigger control down. Really concentrate on your breathing and pay attention to when you seem to jiggle most. Really concentrate on trigger control and getting that slow squeeze down and being suprised by your shot. Then work on staying in the scope (if you can) and getting prepared for a follow up shot and on target quickly.