If I got in a fight on school campus and am now being charged with third degree assault, what do I do?

Given the fact that you now are facing criminal charges where if convicted you could end up being jailed you should consult with a criminal defense attorney to assist in your representation. My experience is that with criminal matters one should always have a competent criminal defense attorney as opposed to trying to resolve the problem on his or her own.

Retain an attorney to help you. Depending on the circumstances, there may be defenses available to you, such as self-defense (e.g. if you can show someone else attacked you); even if not, if you otherwise have a clean record, you may be able to get the charges dropped or reduced, and/or minimize the punishment--especially if there are other mitigating circumstances, or if no one was badly hurt. However, an experienced criminal defense attorny will be much more successful at doing this than you will be; let an expert help you.