You may not be able to stop "bullying behavior" completely, but you can definitely discourage it with some of the following suggestions:
Bullies love an audience - so don't give them one if you can avoid it.
Use confident body language that is not threatening but gives off an assumption that you are not going to be mistreated or intimidated.
Ignore the bully, offer a look of surprise or pity and move away from the threatening behavior.
Always keep your composure, stand your ground and never get emotional.
If you have the opportunity, and it is safe to do so, try to separate the bully from the rest of the "audience" and address the behavior directly. Speaking to them in private will make them feel less powerful and put you on even ground.
However, do not isolate yourself from the group. Doing so could not only give a bully the opportunity to attack you, but may also cause others to avoid you for fear that the bully will redirect and target them.