I guess the best solution to avoid scammers are stay away on it, use your mind and think many times before making moves, also use an escrow or middleman so that you manage things to the one whom you transact with, there lists of escrows here which is reputable, also always bear into your mind that if it is too good to be true then it is not.
Sure, this is true but the problem with that is that scammers can be anyone -- even people you have dealt with perfectly before. I don't think it's valid advice to tell someone to simply stay away from scammers. Using escrows and middlemen are agreeably one of the best options that people have; however, your bit on staying away from scammers is almost like saying don't deal with anyone at all if you want to protect your money.