It's the ones you don't notice that are the most dangerous. Here's how to avoid being hustled, whether you see it coming or not. If you don't gamble, you can't lose. If you can follow this rule, you won't need any others. Bet only with people you know.
Hustlers play characters like wolves wearing sheep suits.
Quit while you're ahead. Good hustlers will let you win a game or two to build your confidence, then get you to double the stakes. If you suspect you might be being hustled, finish your game and make up a very good excuse. Keep an eye on players eager to bet and more eager to raise the stakes. It's generally an unwise investment no matter how good it looks.