The easy way to remember how to use them is remember i mil=36 inches at 1000 yards or 3.6 inches at 100 yards. If you know how big your target is, you mil it to learn how far away it is. Conversly, if you know the distance you can determine the size. Stay away from any variable mil dot scope that doesn't zoom the reticle with power changes. They only work at one power setting, usually the uppermost. A few scopes, such as Zeiss, Weaver tactical, Leica, etc. zoom the reticle with power changes. Those are much more foolproof, but I only will use fixed power mil dot scopes - no guesswork. Once you learn how to use them they're wonderful tools but do take some practice to learn.