Originally posted by kestar:

Originally posted by Jitatha:

I just put a red cross on those I have explored

I take my mace out and destroy the green lamps at the entrance to mark an already explored crypt. That way I already know visually without any extra map markers

But sometimes they get destroyed when fighting whatever may be "guarding" the crypt.

I use the red cross method as well, also with burial chambers and troll caves. It's the easiest way when it comes to using the map.