Don't leave a single candy wrapper, dead battery, or anything else you brought into the cave. Always remove other people's trash when you find it. Ancient artifacts, on the other hand, should be treated with the same respect as the formations themselves. If you gotta go, you gotta either hold it until you get out, or pee in a bottle. We're serious here.
Human waste breaks down very slowly, if at all, in caves.
If you took a leak six months ago, it may still smell six months later. Never touch any formation, especially with bare hands. Besides being fragile, the oils in your skin will halt the growth of formations, and in the worst case stain them or wear them down. Don't bother the wildlife. In particular, bats can be very sensitive to being woken up and can die.