Well, any enemy may kill me, I have a bad habit of going too fast in the dungeon and thus accidentally running towards a floating eye...
Try keeping your pet, and let it fight for you. In early stages, your pet fights better than you, even for combat wombats like Barbarian or Valkyrie. A pet could save you, or when against very tough opponents, at least buy you some time to run. With each enemy your pet kills, it grows stronger, and later on you could polymorph it into something really useful, like a dragon or a purple worm (a D&D monster, a super huge worm with a big mouth that swallow you whole). Also your character level is part of the equation in the monster generator - the weaker you are, the weaker your enemies will be.
Well, I'm still in the phase where food is the biggest problem.
A pet could answer some of your questions... make a new character, and observe what the pet eats and what it doesn't. *Almost* all corpses your pet eats are safe for you to eat, with a few notable exceptions -- bats and rats. Common sense would tell you not to touch those.
Having pets come with a few catches, though.
The first catch is to keep your pet close... most people gave up their pets because it takes them ages to get them to follow or get into where they are needed.
The second catch is food. Carnivorous pets like cats and dogs are forever hungry... they eat nearly everything they kill. Having them around means very little food for you.
Solutions to the first:
1) Leash. You can #apply it to your pet, keeping it no more than 2 squares away from you. If you walk in an opposite direction when your pet's already 2 squares away, you yank the leash and your pet becomes less tame... so wait for the pet to move closer if that's the case. The catch: cursed leash will strangle your pet.
2) Whistle. You can #apply it, producing a high whistling sound. Your pet will try to move closer to you for a few turns. The catch: it might wake up something else in the dungeon.
3) Tripe ration. By keeping one in your open inventory (i.e. not inside other containers), your pets will be drawn to you like magnets. The catch: none really, other than you need to pick it up before your pets devour it.
4) Magic Whistle. The ultimate solution to pet problem. It won't wake up other dungeon inhabitants, and it will teleport your pets to you, within one to two squares. The catch: Watch where you use it... you might teleport your pets onto traps.
Solutions to the second:
1) If your character starts with any food, make those your emergency reserve. Eat corpses.
2) Sokoban. Besides the prize at the end of the dungeon branch, there will be lots of food in there. In the main dungeon, you will find a special level with a huge room... inside there will be a bunch of statues, with a small room in the middle. The small room has 4 fountains, with a special NPC inside - the Oracle. That's the Oracle level, and the level directly beneath it will have *two* upstairs. One lead you back to Oracle level, the other into Sokoban.
3) Stick close when your pet fights. If your character is faster than your pet, you have a chance of stepping onto the corpse first.
4) If you find a shop with food, buy or steal them.
5) #pray. If you have no other problems to fix your god would make your stomach content. Don't do it too often... your god doesn't like you to boss him/her around. For a low level character, it's about 600 turns between praying.
6) If you're playing a healer, they start with the spell Stone to Flesh. You won't be able to use it until you're level 3 because of insufficient MP, but once you do, you can zap a boulder with it to create a huge chunk of meat. Eating one could be dangerous though: you can choke to death. So if you're to eat one, make sure you're at least weak (or very close to weak) from hunger.