Here’s a good idea from Defender88 at the NRA’s Shooting Illustrated:
“Buy a stack of man size silhouette targets.
Take 1 and make a large x across it.
Indicating this is a Non-Threat target.
“Staple the non-threat across the front of a standard threat target. Cover 1/4, 1/2, 3/4 of the threat target. Practice moving and shooting and hitting the threat (say head shot) without hitting the non-threat. At different distances.
Find out what your real capabilities are, under ideal conditions. Considering how you would feel in hitting a non-threat : Wife, kid, by-stander.
Try making a head shot, while moving, with one hand, etc.
Then consider it will be 10x harder in a real fight.
One thing more important than knowing ‘when’ to shoot is knowing when ‘not’ to shoot.”
And, having practiced, being ready to employ your knowing.