-Meat obtained from enemies that isn't cooked can be frozen or burned and become edible.
-Pastries restore more food than the rations can.
-You will always land an attack if you lead an enemy into a doorway, even if they are one cell away from you, but the door cannot be burnt.
-If you are unsure whether a potion is safe or not, throw it against a wall. Most potions like poison or gas will reveal themselves if thrown and you'll always know when you get one from then on.
-Cursed items lose the curse if improved with a scroll.
-Anointing the Ankh with a full flask of water will make it more powerful.
-Enemies that are faster than you can hit you even if you move away from them.
-Yes, water can eliminate the effects of fire. Also, fire burns.
-All doors in a level can be accessed one way or another.