Tips for taking better food photos- #1. Don't Be Lazy!
I know, I know... you already thought of this. But look around the web or on Instagram and see how little effort some people put into taking food shots. By just putting in a few minutes of thought and a smidge of practice, your images will improve dramatically. In a restaurant, get off your butt and move around if you need to. Ask for a table close to the window if there's still daylight outside. Use natural light if possible. Or, actually go outside. Most ambient light (available light- think spotlights in the ceiling) in restaurants is either too dark or too harsh. Window light is perfect. And, lighting is everything. Literally the word photograph means light (photo) writing (graph). Learn how to use it. Learn how to bounce, diffuse, and reflect light. When you are ready, learn how to use alternative light sources like a flash or LEDs as well.
And never, never, never cast a shadow into your image (See Yelp image). Before you hit the shutter button stop and look! Don't be lazy!