I've heard a couple of food pro togs talk about their art.
Use flash because it's reproducible. The whole menu looks consistent, and when you come back in three months time because some new dishes have been added, the shots fit in with what's happened beforehand.
The basic idea is a big soft light from one direction only, with some fill from the opposite side. It's important to do this to reveal the texture of the food, there must be shadows and highlights.
Dark brown foods are a problem, they look like ... um, I won't say it, just unappealing, so you must expose for those highlights.