1. Don't be too hungry
That old adage of not going to the supermarket on an empty stomach holds true for the buffet. Megatoad says it's best to "not starve yourself" going in, as that can lead to having your stomach cramp up when you fill it with 10 plates of sliced roast beef. He recommends eating a light meal beforehand, like yogurt or a bowl of cereal, as they'll "move quickly". Yes, that means what you think it means.
2. Act mental
Megatoad advises against going to a crappy buffet just because it's cheaper, as you'll end up being disappointed. Once you find a place you like, ask to see the food, and "get mentally psyched to destroy it". Act like Ray Lewis used to before a game and go HAM in front of the ham.