Took a shot at a doe 3 years ago, Thought it was 90 yds, Using a slug with a rifled barrel I lead it what I thought was about 3 1/2 ft. Well the end up was it was 110 yds, and the deer piled up 5' after the shot. As far as practice, shooting clays wouldn't hurt.

Lead all depends on how far the deer is, how fast it's running and as others have said what your shooting. Some where on line I read the amount of lead to allow for under different conditions, and the speed at which a bullit or slug will travel in relation to the deers speed,and distance. Now I'll have to search for it.