There are a variety of reasons that might mean your dog struggles with guests coming into the home. Perhaps it is due to genetics if they are a guard breed, lack of confidence, territoriality, under-socialisation, over-socialisation, anxiety, or fear. No matter the cause, it is almost always best for those entering the home to act neutral and non-threatening towards the dog. If your guests directly approach, make eye contact, reach for the dog, hold the dog, talk to the dog, lean over the dog, etc., they are only confirming for the dog that they are a threat and the dog will act accordingly. The other issue is that a lot of the time when you tell a guest to “act neutral” or “ignore the dog”, they instead act stiff and awkward, which likewise puts the dog on-edge due to strange and uncomfortable body language. You need your guests to act as they would were the dog not there at all – this is really hard for a lot of people and guests often disobey the instructions given. When this happens, it adds to your dogs history of negative experiences with guests and makes it harder to break them of their habits towards guests in the future. If you really struggle to get guests to listen and follow your training protocol, then you need to consider putting the dog in their crate or in another room entirely to avoid interaction when you cannot guarantee that the interaction will go as planned. Pick your battles.