1. Lighting is important.
Window light is a great light source. It is large and when diffused it can wrap around your subject nicely. When you’ve got harsh light coming through the windows, incorporate shadows into your composition.
2. Composition is everything.
Since the food is the star of the image, limit the distractions in the background. Using a fast lens will allow you to use the shallow depth of field to your advantage in throwing the background out of focus. Turn the plate around so you can see which side is best to shoot.
3. Keep it simple.
When you’re shooting in a restaurant, be polite to servers and fellow diners. Stick to available light. Bump up the ISO if you have to and shoot at wider apertures.
If you don’t like the images once you get back to your computer, but do like the subject matter, odds are the dish will still be on the menu when you return.
This is easiest when you’re shooting in your own kitchen. Use an eclectic collection of dishes or glasses; experiment with the lighting, or by changing the white balance to alter the mood of the image.