I saw this on the forums:

How to tell if one is a bot/farmer in L2:

"Theres a lot of ways to tell. First off, they're probably a dark elf, maybe light elf, with manticore and a maingauche. Sometimes dwarven scavengers (this changes sometimes obviously). They also usually have a stupid name. An example would be oo00USA00oo, llllapplellll, lovehavegreat, eelove0133, happy003, etc. And if the word "love" is in the name somewhere 9/10 times it's a farmer. In towns they usually have stores up that say "LOOK LOOK LOOK." Don't support them by buying from/selling to them. Also almost anyone who says ++++HP unless they're joking around. And of course 99% of the people in low level dungeons..."