If your dog has a sensitive stomach, make sure you only make gradual changes to his diet. Abrupt changes will make the diarrhea worse.
No people food. For a dog with stomach issues, it's overly rich.
I personally like Royal Canide's Sensitive Stomachs. :) But it'll be hit and miss until you find one that works for you. It may take several weeks for the dog to be completely switched to a new food. Do it gradually.
Also, have your dog checked for health issues as well such as worms.
If the diarrhea persists or is bloody, a vet is a must see.