Bullies are just insecure morons who have to scare people into being their friends. Usually if you stand up to them they will back off and leave you alone. This DOES NOT mean you should fight them, they aren't worth getting in trouble for. But I've learned that if you stand up to them they will usually back off because it's no fun for them if they aren't scaring you and they will move on to someone else. If it gets out of hand I'd let an adult know about it though.