I give out treats after grooming, and first thing in the morning when they wake up. I used to treat a lot more, but I've cut down as Nikki has gotten older.
If I am training them, I will treat.
I give out tiny pieces of fruits/veggies or meats, either fresh or dried/dehydrated, either from leftovers or Plato brand organic dog treats.
I used to treat with Cheerio-type O's cereal, but now only give them rarely, as we're moving toward being a completely grain-free household.
I think as your dog gets older, cutting down on treats is a good idea, especially if they are higher carb treats.