Dont use anything that you would be able to notice on someone else in less then 5 seconds of watching them. So obviously no aimbot or speed hack. Wallhacks encourage you to aim through walls so try not to use them if you cant control yourself.
Dont spend more then 2 hours on a single server because people start watching you if you're always on the top of the list. If you're one of those people thats awsome at games without hacks and you're unstoppable with hacks then keep switching servers because I get banned from servers not because people "know" Im hacking but because my scores suggest I am.