Also what level range you are in.

Generally though I tend to find a few high level mobs that won't kill you. Eg those that have only 1 attack and no lag skills. Or those that are just weak for the amount of exp they give.

At higher levels you might want to focus more on the vuln exploitation. Back in the day I quite often ranked aps on arials that were evil so as to exploit their lightning vuln. No exp bonus for killing goods but was still a decent option.

The tip Isildur gave though about using mobs that drop stuff you can quickly barter for a heal is good, since you get extra exp for the bartering.