If you feed your dog table scraps then you should stop now. This can cause your dog to be a picky eater. The best thing to do is buy a can of a few different kinds and try it until your dog eats one of them.
Try a dog food that is high in protein. My dog was also a picky eater and I switched him to a brand called Fromm's. You can find the brand online or visit a specialty pet shop. Larger chains like Petco and Petsmart don't carry the brand.