If it's something crazy like, he/she is hitting on you or flat out lying to you about something important, you probably have to go higher up because his/her antics are almost certainly well known and accepted by their coworkers and immediate superiors.
If it is something grade related, you may be better off going to the head of the department who will be much better qualified to evaluate the difference between a fair and unfair grade then someone outside the department.
Either way, it’s going to take a lot more then your word to convince anyone that the professor has done something wrong, be prepared to provide lots of evidence to support your case.