Play the wind. Try not to make too much noise. A loner or a sentinel in a group will often freeze, listen, and sample the air, then continue. That is often my target hog because they are looking out for themselves and/or others and are the ones most apt to bust me. Shoot it. During the freeze is often a good time to shoot the hog. You may be able to watch it freeze 2 or 3 times before you see a pattern. The freeze often doesn't last long so be ready to shoot when you see it repeated.

As Oldtimr said, make sure they are dead. When in doubt, shoot them again. A hog that is down and doing the curly shuffle may not be ready to die. I have seen several get up after kicking for a while. Be ready to shoot them again. Also, few hogs die right side up. If the hog is upright on its belly, it is probably still alive. Shoot it again.