I love going to beard competitions and meeting new people and having a blast. Beard competitions tend to be laid back, but the larger events are a little bit more serious with higher expectations for categories and contestants.
It's best to do your research ahead of time. If you are going to an event, try to reach out to past beard competition contestants and get the lay of the land. It's fun to dress up and pull off a total look - rather than just a beard. Take the time to make your beard look the best possible.
More than all that though, try to have some fun and bring some cash to donate to charity. Most clubs are putting on events to raise money for the community and it's a great way to support others.