I use Teddy's unsalted Old Fashioned Peanut Butter. Make 2 small "meatballs." Hide the pill in the first one. Offer teh second one while the first is still in the mouth; so it has to be swallowed as the dog is after the second.

Does not work for Clavamox. Clavamox has an odor which they detect. For that, I do what Karen listed.