First advice: Don't cross us.
If you see a beautiful women, unarmed, unharmed, somewhere in a dungeon, kill her. Don't attempt to converse, don't hail her, don't ask if she's alright. Kill her. Nine times out of ten it's a disguised/polymorphed bad guy. In the rare case where you kill an actual innocent woman (like those are still around *chuckles all around the table, pouting from the priestess*), she was doomed in that dungeon, anyway.
If you find 10 doors untrapped, check the 11th, anyway.
If the rogue says that he finds no trap, always assume he isn't good enough and proceed with caution.
When in doubt, empty a quiver. If it still stands, empty another. But if it still stands and smiles, get the hell out of there.
"A man of honour to the end" looks good on a gravestone, but always consider if you'd rather live.
Saving up that fireball for later will mean that it will never be used if you don't survive.
If you hear a noise, investigate with the whole party. Don't send one man to scout. And if you hear something ten times, and ten times it was nothing, don't assume it's nothing the eleventh time!.