I've got a scoring ring sheet, on a score card holder.. But to tell you the truth, I NEVER use the thing.
The best "cheat sheet" for finding the scoring rings on a 3D target is a good pair of binoculars.
Locate the rings on the target, pick a spot you want to hit relative to something on the target (such as a muscle bump, a paint spot, or even a shadow or a spot of sun on the target) and use that as your aiming point. Works great for me.