When we first adopted Roscoe we used a regular collar. It wasn't that big of a deal while he was 10lbs but soon his weight doubled and then tripled. Now that he weighs over 30lbs walking him on a regular buckle collar is an unpleasant pulling match. My dad tells me often that he likes the added challenge of his Irish Setter constantly pulling out in front of him and deciding without warning to pull this way and that. It is very true as he says that they both do much more physical work in a shorter amount of time but his dog, Copper, is also learning that if she pulls hard enough in one direction she'll get to go where she wants even if he doesn't want her to go there. A walk like this also cements the relationship as one which puts Copper's wants above my dad's, making Copper the master and not my dad.
Now that you know the bad results of letting your dog drag you all over creation I will share some of the benefits to having a dog that can walk next to you on a loose leash and how to achieve this. First of all you far more likely to want to walk your dog if you don't have to play tug-o-war the whole time. This will make you want to go get some exercise as well as exercise your dog. Second, if your dog walks next to you on a loose leash this means that even though you aren't in your house your dog still is looking to you as its master. My third point is a combination of the first two, since you are more eager to walk farther and longer you are able to maximize the time the two of you spend cementing a wonderful dog/master relationship. The more respect your dog gives you while walking the easier it is to transfer that respect into the rest of your relationship in public places and at home.
Now that you know the benefits of having your dog walk on a loose leash next to you and not in front of you I will give you a few tips that you can use to make this happen with your dog. First the type of equipment you use and making sure you use that equipment correctly can have a huge impact. There are three major types of equipment designed to give you more control over your dog. These three options are head-collars, slip collars, and no-pull harnesses. A head collar works in a way very similar to a bridle on a horse. Rather than attaching the leash to the base of the neck where the animal has a lot more strength you attach the leash under the muzzle where the animal has less strength. If you capitalize on the dog's weak spot you increase the effectiveness of your own strength. Now that you have the leash attached in a way that gives you the advantage I will explain how this benefits you.
As the dog starts to pull to the fullest extent of the leash its head is forced to turn back toward you, the master. This redirects the dog's attention off of whatever it was pursuing and back on you. Also as your dog starts to walk with a loose leash corrections are much easier to accomplish when the dog "forgets" what it is supposed to do. A simple flick of your wrist will accomplish far more that trying to pull a dog with a buckle collar.
Second I will explain how a slip-collar works. Slip-collars are often known as choke chain, but this name is misleading because if properly used you will not choke your dog. With a slip-collar you are able to adjust the position of the collar from the base of the dog's neck by the shoulders to the top of the neck where it meets the base of the dogs head. The idea is similar to the head-collar. The slip-collar attaches the leash to a weaker part of the dog's neck so you don't work as hard and you have better control with better results. As the dog starts to pull give it a quick pull and release immediately, making sure the collar is positioned so that when you release tension the collar slips and becomes loose again.
Third, is the no-pull harness. This is a harness that has the leash attachment at the dog's chest rather than its back. Like the head-collar, the dog is forced to turn back to you when it tries to pursue something and it allows for quick and easy corrections for the same reason as the head-collar. The advantage of the n0-pull harness is that a dog that constantly fights the head-collar which is around its muzzle will still most-likely accept a no-pull harness which has no parts near the dog's face.
Of these three I prefer the head-collar. I don't like how harnesses look and I don't like the stigma of choke chains. This is purely an opinion. All three work very well as long as they are used properly.