My mom is so good at this. Knowing who gossips, knowing who is actually trustworthy, and knowing who is too ignorant and filled with drama to recognize a lie when they hear it...all you really have to do is watch who they run with. It's so true. You should judge a person by his/her friends if you want an accurate portrait of them. e.g., if your friend has done some awful things to someone, and you're still friends with them, you're just as bad. Birds of a feather.