In order to move off an edge: Alt+(movement key) WARNING! If you do not have skill in swimming, you
will drown.
In order to refill a waterskin: Stand next to a water source (you don't have to be in it or on top of it), and press Shift+I. Select your waterskin in the opened menu, and then select the water source you want to collect from.
Corpses cannot be eaten, sold, skinned, cooked, or anything else for that matter. The number that appears is the weight of the item, not the cost. Adventurers have no idea how much anything costs, you just have to make educated guesses.
The only way of cleaning yourself is to jump into some water. Again, not recommended unless you can swim. You can train up swimming skill in a relatively safe environment if you're lucky enough to find a waterfall. Stand at the very edge of the cliff the waterfall's pouring over, and then walk into the shallow water just where the water runs off. Then attempt to walk upstream.
You can get emergency food supplies by pressing Shift+L and "l"ooking around for small creatures such as lizards, rats, large cockroaches etc. These you can eat when you become very hungry. Otherwise, the only place to get more food is from human cities.
Anything else?
EDIT: Oh, and this should really be in the "Gameplay Questions" section.
[ May 16, 2008: Message edited by: Kagus ]