*WARNING WARNING WARNING!!!*
DO NOT LET HIM USE HIS BEAK TO GET HIS WAY! If you allow your BG to know that he can get his way by using his beak you are going to have a lot of training/behavior issues (not to mention DOCTOR bills, and I am not talking about the Vet). Remember, you are in charge, a "STEP UP" command is that, a COMMAND THAT MUST BE FOLLOWED!
I can't stress this enough with MACAWS (especially multi-homed macs) you must let them know that YOU are in charge. Set ground rules for acceptable behavior and non-acceptable behavior. THE MOST EFFECTIVE FORM OF PUNISHMENT for a MAC is to IGNORE THEM. These birds are HIGHLY social and thrive on human interaction. If he steps out of line - BOOM ON THE FLOOR and TURN YOUR BACK - Let him know who is in charge and you will have a great relationship with your new friend.