I find that anything that isn't especially made for dogs works best and is often healthier too.
Indoors I tend to use kibble (unless teaching something new) as that is enough in that environment, but in classes our outside it's got to be better stuff like sausage, frankfurters, cheese, ham, cooked meats, dried fish etc.
You might also find that you can use different value treats depending where you are and what you are doing. The general rule is that high value treats are needed when:
1. Teaching a new behaviour
2. Practising in a new environment
3. Increased distractions
When people come to my classes, I give them the following exercise to do to find out what their dogs will work best for in the classes:
Take 5 different types of treats out with you (not pet shop treats), then wait until your dog is REALLY distracted. Then offer each treat in turn and see which ones your dog will eat. The ones they do, you bring to class.
