My Jack always gets really excited when playing and tends to nip and bite a little, but really only Me and DH (not guests or anything) what has been working for me is putting my hands on either side of his face and saying in a really low growling voice "no biting." He usually stops. If he is really wound up and won't stop after this, I give him a time out in his crate. Yeah, I know he isn't a kid, but I kinda feel that if he keeps going I might just lose it on him, you know, yelling….and I know he doesn't respond to that- he just looks at me like I have lost it.
I don't really know if this is "right" or not, but it works for me. I tried the "Ouch" really loud, and redirecting and stuff, but it hasn't been working.