Hi D. - First thing, make sure that you and your husband's form of discipline with your son is NEVER hitting, even on the bottom. It would be extremely difficult to teach him not to hit if he gets hit when he does something wrong. My daughter had trouble with biting other children when she was that age...unfortunately, the only thing that FINALLY worked (just before she was kicked out of daycare) was to bite her back...that's right...she bit me on the arm and then I bit her back on the arm at the same place she bit me. She then looked at me with amazement like "wow, you hurt me!" and then I said firmly "no biting". That was the end of the biting for her. The problem was that other children never bit her back so she didn't realize the pain she caused them. However, you can't do that with a child that hits because you will simply be hit back. I think the best thing to do would be what "Nanny 911" teaches and that is: use your firm tone and say "no hitting" then put him in a "naughty chair" (or wherever you decide) and have him sit there for 2 minutes (they said one minute of timeout for how old they are...e.g. two years old = 2 min). When he fights you, get down and his level, look him in the face and hold his arms down firmly, then say "no hitting, use your words not your hands" and send him back to the naughty chair. It will take A LOT of patience and discipline on the part of you and your husband to pull this off, however, CONSISTENCY IS KEY, and it will work!
L. ;-)