So I'm having dinner with the girlfriend's family this evening... Any advice?
Well you see, I don’t have very much experience in that way, myself. I suspect that tidiness is called for- a good grooming beforehand. Perhaps bring a gift, and don’t make eye contact with her father. Unless you are looking to establish dominance and territory, which I wouldn’t recommend if you aren’t prepared to duel.
Oh, and do wear lots of colors. The brighter the better, I believe. Learning the steps to your preferred mating dance may impress her, too.