Train before meals, so your dog is hungry. Remember, also, the DOG determines what is an effective reinforcer. To figure out what your dog likes, get a supply of a variety of treats. Present them to your dog two at a time and make a note of which he eats first. Through the process of elimination, you can figure out exactly what foods your dog most likes.
Most dogs prefer smelly treats like cheese or liver.
Once you have an effective reinforcer, another key to successful clicker training is using the reinforcer correctly. Some people use food lures when they are first teaching a dog a new behavior. The more repetitions you do with the food present, the more dependent on the food the behavior becomes. If possible, keep the food off of your body entirely. Put it in a dish nearby, and actually walk to get it after each click.