Don't pull off!!! My understanding is that is funny to many of them. Everything I have read has said to actually push them into your breast firmly - smothering them and forcing them to break the latch. Then, in a firm voice say no. Make sure not to use a high pitch as many little one's think - oooo, that was fun, I am going to do that again!
My little one did this once and I used the above tactic. He hasn't done it again. The idea is that you make the biting experience as miserable for them as it is for you so that they don't want it to happen again. Be consistent with it - Good luck!
Also, keep a close eye on him. To move to a biting position, he actually has to shift his jaw. Keep your pinky finger near his mouth and if you see the position shift then break the latch before he has a chance to bite. Some also say that their little ones flash them a little look before going in to bite. Hope that helps!