Summarize:

They are always complaining about something, and that's not nice or fair. Don't make eye contact, respond with words or actions, or give any clue that you heard what they said. This may cause this person to go around bad-mouthing you, but remember that you don't want those negative people in your life anyway. Cliques are small, well-known social groups that don't allow new members very often, and they tend to start a lot of the drama at school with bullying and gossip. Even though it might seem cool to be in the most exclusive group in school, don't try to get into a clique that already exists. They'll probably see you as the new target for their bullying. Form your own unique friend groups by finding people in a club or activity who have similar interests as you. Always be open to new members. If someone does something wrong, try to open your mind and think about their intentions before judging them. If they were truly wrong, that person might not be a good friend to you in the future. If someone can't take the hint that you're not interested in being involved, give a polite but firm excuse and leave. "I'm sorry, I have to go" will usually work. If you're stuck with that person in a class or activity, say "I would like to get back to my work now." Repeat this as often as necessary.
Avoid negative or dramatic people. Skip the clique. Be intolerant of hurtful behavior. Have an escape plan for difficult situations.