Your dog may be more food motivated than you think. In training we talk about the value of treats, low value treats might be the kibble they eat everyday, vs high value treats that include chicken, cheese, hot dogs, steak, etc.. It takes a bit of trial and error to find what you dogs likes most. My dogs like carrots, frozen bananas, string cheese, chicken to name a few. It's important that the treat be cut up into small pieces. Personally, I like Zuke's Mini Naturals. They are small, 3 calories, and ,most dogs like them. Try to avoid working with your dog after meals. It is best for to feed about an hour after training.
Start leash training in your backyard or in the house.Use a treat to keep the dog at your side. When the dog begins to pull, stop and have the dog sit. Use a treat to keep the dog's focus on you. If he keeps pulling, make a U-turn with the puppy on the outside of the turn and head in the other direction. Don't wait for the puppy, just go. Walk about 30' and make another U-turn. You may need to take walks that are a constant U-turn up and down the street for 15 mins.
Good luck.
Try to find your info http://www.labrador-retriever.club/labrador-retriever-training-tips---the-complete-guide-3650 (Here)