The act of back-stabbing is not a difficult task.
It is to earn someone's trust, by becoming their "friend" or otherwise, and then break it repeatedly.
It's easy to tell who's a back-stabber and who's not. If:
1. They talk bad about somebody else that they seem to be close with,
2. Many people don't associate with them for the fear of being talked about,
Or just seem like a bitch in general, watch out. These are sure signs.
Just a few examples of back-stabbing are if they:
1. Tell everybody in your grade that you are pregnant.
2. Talk behind your back about your strange behaviors after the death of you dad.
3. Hit on, go out with, and be a total slut to the man you clearly like, and that she has bad-mouthed repeatedly in the past.
4. Start numerous rumors about how much of a "fuckin whore" and a "piece of trash" you are.
After this, they will most likely come back begging for your loyalty to them.
This, in some cases, is acceptable. But be careful, it's bound to happen again.
~ ~ ~
"Woah, dude, did you hear that Lauren's pregnant?"
"Nahh, man, that back-stabber Annika's just starting rumors."