Most kids either have been bullied, know someone who gets bullied, or are bullies themselves. Sometimes all three apply to the same kid in different situations.
I'm a great fan of Izzy Kalman's suggestions on how to handle bullying because I've seen his methods work in my own life.
Kalman is Jewish, but he bases his method on the teachings of Jesus. Kalman believes, and has evidence to show, that turning the other cheek really does work.
Tattling or seeking revenge just make the bullies try harder to dominate whoever does those things. Of course in a severely dangerous or possibly life threatening situation it's sensible to get help, but most of the time simply acting like what the bully does doesn't matter is the best way to handle him or her. (And, yes, some bullies are girls.)
It means they've lost the game.
Bullies are people who need to make others feel bad in order to feel good about themselves. If they don't get the reaction they want from a victim they'll try harder for a while, but then they'll give up on bothering that person.
And bullying isn't just physical or only something that happens between kids. Adults can be mean to others in many ways.
If you know anyone dealing with bullies I recommend checking Kalman's website for helpful information. Here's the link: http://bullies2buddies.com