Something I wish I'd learned much sooner: From birth, be unfailingly patient, warm, and loving with the little bugger, no matter how frustrated you might be feeling. Matter-of-factly communicating unhappiness with him* is fine, but never, ever get angry with him — when he's "misbehaving," talking back, etc., it's because his brain and its "programming" are still developing and he doesn't have nearly as much control as you might imagine, or as you think he ought to.

* Or her, of course.