18 months.... this is the perfect time for this type of training. He's still a juvenile and he's trying to figure things out on his own. This is a crucial time for him to have a hierarchy in place (you as the pack leader, then your girlfriend then any human then him)!! Try this: 1. Have boeda on sit next to you with a prong collar and a loose but short leash and have a treat on hand. Have a stranger walk straight up and stop at about 3-5 feet from you and say hello. Wait about 20 seconds like that then have the stranger walk away. If boeda seems in control and doesn' t show any signs of aggression, give him the treat and praise him like hell. Try this for a few training sessions and only praise him and give him the treat when he's calm and shows no signs of aggression. If he growls or lunges, give him a swift correction with the prong collar immediately or as you see him begin to display the unwanted behavior. 2. Have the same set up as the first step. Once he's mastered the first step, have the stranger carry a treat with him. When he walks up to you have him extend his hand (the one with the treat) as if for a handshake. If boeda even flinches towards the stranger or growls or shows any sign that he will become aggressive, correct him immediately and have the stranger stand still (you do not want boeda to associate a display of aggression with the stranger leaving). Once boeda is calm and relaxed next to you, the stranger walks away!! (He must only walk away when boeda is still and calm!!) Do this until the stranger is able to shake your hand and hand you the treat. If boeda allows the stranger to shake your hand without showing any signs of aggression, immediately when you shake the strangers hand give boeda the treat that the stranger brought with him. Do this for several sessions after that! After boeda associates the stranger coming towards you for a handshake with a treat and a praise, you'll be all set. Eventually eliminate the treat and only praise him and in a few weeks you'll have a dog that will allow any non-threatening human approach you for a handshake. Eventually you might want the stranger to hand him the treat, but that is up to you! Personally I did that when my dogs were 8 months and below. Now if I allow it, my dog will allow any person come close and pet her. However, if I don't know the person I normally will not allow he or she to pet her because I want her to welcome whomever I welcome, not EVERYONE!! Hope this helps and remember that 18 months is just a pup! ALV