Cutting off the ring isn't too difficult for a guy that has a decent punch. If your opponent moves to his left, you throwing your right, will automatically force him to move to his right, 9 times out of 10. When he moves right, you throw a left hook, which forces him to move to his left again. Essentially this keeps him in front of you as long as you keep doing it. Of course there are exceptions, but against a beginning fighter, these should work well. Whatever direction he moves, you throw a punch with the hand closest to the direction, to force him the other way. Body punches are especially good for this, because they are nearly impossible to slip, which means you'll get resistance each and every time stopping them. Julio Cesar Chavez was great at cutting off the ring. He'd stop an opponent moving to the right, with a left hook to the liver, and he'd stop an opponent moving to his left, with a right hand to the head.
Thanks, Hope your other ones are just as good (the ones I requested :-) )
technique posts are money. Keep 'em comin'.