Yes, food is the most common reward. There are other methods that many behaviorists advocate, but there's nothing wrong with using what works.

Another important thing is to never, ever, ever call your dog and then punish them when you get your hands on them. It will quickly destroy all your good work. I'm opposed to negative reinforcement anyway, unless you can catch the dog in the act of an unwanted behavior. I never struck my female once in her entire life and I intend to follow the same practice with my male.