Like other people have posted its just practise, practise, and more practise. Once you pick a method, like stopping when he pulls, stick with that method! If you let them get away with pulling one time, they will try it whenever they can!

It's a Halti harness it's not the one the goes over the nose it's a regualar harness but it works great it hits a pressure point and they don''t pull you can get it any pet store it's alittle expensive like $28.00 but it's worth it
I have heard that these haltis can damage your dogs sense of smell after awhile, and don't really solve the pulling issue. Its just a bandaid, covering the problem, but not fixing it.