You need to make a lasting first impression. Show them you are kind, but firm, and will not be intimidated. Walk in with some casual clothes, kick off your shoes, and be sure that your very first words are, "What kinda crap we eating tonight?" Sit down at the dinner table, try to tell the wife how she can improve her cooking, and offer pointers and advice. This will show them that you know what you're doing, and that they are in the presence of a superior being.
Once you have them eating out of your hands, you should join them by shoving food into your mouth as quickly as humanly possible, leaving little for them. The bigger the portion, the manlier your image. Drink directly from the gravy boat and let it dribble down your chin. Grab your girlfriend and start making out with her right there. Make fart jokes.
