Just keep your wrist as straight as possible and try to bend their wrist as much as possible... Also sledgehammer training will work your wrists and forearms. I think it's mostly hands wrists and forearms, not biceps.
Article on sledgehammer training:
http://www.rosstraining.com/articles/sledge.html
Kettlebells/clubbells might be equally effective, I don't know.
Also I'm no expert but I finally beat a guy for the first time.
