When fisting someone there are three things to keep in mind:
1) Always trim the nails, always, many blood vessels run on the inside of your body (duh) and they can get cut.
2) Unless you have a hyper salivation disorder (as I do) use as much lube as-
-possible it's very dangerous to dry fist.
3) Unless you're into scat make sure you're doing deep enemas, eating light, and avoiding fiber rich food. Fisting is going very deep and that means you'll need to be deeply cleaned.