Robert has the perfect video for this when you first start working with a dog and you want him to follow you. He is at the shelter and working a black pit bull.
1) start by giving the dog a couple of treats, you want him to know that you have something he wants 2) give him more leash 12/15ft you can shorten later 3) do not correct him while looking at him. 4) when the dog starts to check out make an abrupt turn in the opposite direction (no talking) when he catches up Good Boy, treat 5) Also when he starts to check out Heh! when he turns to look show him treat 6) Sometimes you can stop, if the dog sits next to you and looks at you Good Boy, treat.
These are just the basics, the video is more detailed. We are conveying to the dog that being close to you is a very good place to be away not so much. In this exercise the dog is correcting himself. Also watch the leash position. The way you are holding the leash Robert would make you do 20 push-ups. You are doing very well, keep it up.