To learn the difference, break a berry open. If you are nervous, don't do it with your teeth. Use your fingers but don't worry, they aren't poisonous. If the berry is a dry whitish mealy thing inside with a brownish seed in the middle, you have kinnikinnik. It will be a little bitter, but that's okay, because you won't eat them before you get them home.
Cranberries are the easiest berry to find.
Pick what you find, and take lots of plastic bags or pails to keep them separate. Aha, now we are talking about habitat. Just like other animals and plants, berry plants have specific conditions that they need for growing. To get better at finding berries, you have to figure out their specific habitats. Starting with low bush cranberries and mossberries, look in spruce forests.