My niece stuttered for a phase when she was 2. Her pediatrician said it was completely normal during language formation and basically not to make a big deal out of it. DON'T complete his sentences/ finish what he's trying to say - let him do it, no matter how long it take. Don't let other kids make fun of him (my niece has an older sister!). Basically don't point it out to him (obviously address it if he's concerned, unlikely) -- and let it take its course - it'll go away.