If you have a new puppy yhat is showing real signs of aggression, the first thing you need to identify is why he is aggressive.

There are basically four types of aggressive puppy.

The first one is Dominance Aggression. This usually occurs when your puppy is in a social environment where there is no control and he is trying to take the lead.

The second is Fear-Motivated Aggression. This is usually when your puppy feels threatened in some way.

The third is Territorial Aggression. Your puppy will feel the need to guard his territory, food bowl, toys etc.

Lastly is Protective Aggression. Your puppy is feeling the need to protect. This normally means you and or members of your family.

The best dog training advice I can give is to observe his behavior and act accordingly.