Originally posted by electricdawn:

1. Eat the best buff food you have available.
2. Go fully naked. NOTHING in the inventory.
3. Turn off auto-pickup by pressing V. Wait for the message to appear that it is really off.
4. Sneak as close as you can.
5. When the boss starts to notice you, press V again, RUN LIKE HELL towards your gear!
6. Pick it up and IMMEDIATELY run away from the boss as far as you can.
7. ...
8. Profit!

Edit: I've done this countless times, and I can vouch for it to work. When you just picked up your gear, you get a corpse run buff, meaning your stamina drain is very much reduced. You can run forever. Use that capability and get away as far as possible from the boss. Of course you should be aware of your surroundings and don't run into unexplored territory where you will die to a... mosquito. Yeah. ;)

1. In my world there is a lot hills and mountains, I simply can't run away fast - there is no straight way. I can run until I reach mountain or river and then boss kills me, because he doesn't care about obstacles.
2. I didn't try it with corpse buff yet, but I wasn't able to run away from boss - he is just too fast. Even monsters can follow me for 10 minutes non stop, what to say about boss?