After you have figured out what your cat likes as a reward, lure him into a sit by raising a treat above his head backwards while saying “Sit!”. Reward him when he does it.
Some cats will automatically sit. If your cat doesn’t sit, gently maneuver his bottom down while saying “Sit!” Reward him after he does.
It is very important to train a cat in between naps and, if treats are used as rewards, when he his hungry.