Training your big dog to walk on a leash with you instead of pulling you will be imperative if you ever plan to take your large breed out for walks. You need to make sure you have complete control over your dog so he does not pull you along, become distracted chasing a rabbit or squirrel, or drag you down the sidewalk, and so that he knows who is master. Your big dog may overpower you way more than you can overpower him, and he may be bigger than you are. Having control over him has nothing to do with how much power you can exert over him. It has more to do with how much respect you can teach him to give you. Training a big guy to walk on a leash beside you will be imperative for most of your additional training to come with large breeds.
Because this training, for large breed dogs especially, is more about your dog knowing his place with you instead of pulling you along a walk, you will need to find ways to encourage him to walk with you without pulling. This may require a special harness, a thicker leash and lots of treats to keep him in your control and wanting to stay with you to continue to earn delicious foods. For your early training sessions, you will need to find places without distractions so you can focus on your dog and your dog could focus on earning treats. As he gets more comfortable on the leash and you are more comfortable controlling him, take him places with minimal distractions so you can see how he reacts when something else draws his attention away from you. You may find for large breed dogs, a harness that clips on the chest rather than on the back gives you more control.
Of course, for this training, you are going to need some incredibly high-value treats. Cheese sticks, hot dog pieces and dried liver treats are all great items for large breed dogs to learn how to walk with you on-leash. Keep in mind just because your dog is a large breed he doesn't need a larger treat. Even the largest of dogs will work hard for the tiniest morsel of food. Check your harness and leash to ensure your dog has proper equipment before you head out for a walk.