Patience, Patience and More Patience
Taking bucks consistently is an art; anyone can luck into a big buck, but it takes work to harvest bucks year after year. Even for veteran hunters, patience is the key.
Deer don't always do what we expect them to. If you have scouted a particular buck and have a good setup, don't force a bad situation. If he comes in from the wrong angle, or even if he just catches you off guard, chances are he'll nail you if you try to move and force a shot.
In many cases the right call is to sit tight and hold still. There are exceptions, of course, and small movements when a buck's head is behind a tree is one. Remember that many things have to come together just right to take a big buck. Don't panic. If you've done your homework, there will be another day.