Don't wear anything too revealing and try to stand near a man you trust. If there's anyone you know well enough, you might confide that you are finding X creepy and request that you stand/sit by this trusted person. If you don't want to be felt up by creeps, don't look unattached and at the same time seductive. i.e. don't convey the impression that you are a) sexy and b) available.
If someone does something fresh that you find distasteful say in a loud voice, 'I'd rather you didn't do that, please' Most times, the creep will feel embarrassment amongst his peers and leave you alone. if there's blokey humour following such a remark, leave it to a quieter moment and make your exit.