One of the most common alternatives to a collar is a harness. Veterinarians routinely recommend that dogs, such as pugs with their short noses, and miniature poodles with their propensity for collapsing trachea wear harnesses. However, it's important to chose the right one. In general I avoid harnesses that hook on the back unless you want to train your dog to pull a cart or a sled. These harnesses actually help train your dog to ignore you and pull you because when you pull on the leash to try to gain some control, they direct the dog's attention away from you.
The traditional way these excellent dogs collars are used by professional trainers is to give a sharp jerk—strong enough to make the dog stop what it's doing and do something else. For instance, if the dog starts to sniff and pull on a walk, you quickly brace yourself and give a quick yank in the hopes that the dog feels it enough to stop pulling. My first trainer told us to generate enough strength by actually running full speed in the opposite direction so that my, then 76 pound boxer, would feel a strong enough pop! The next trainer I had taught me to first attach the leash to a fence so that I could practice the technique and get it right before I tried it on the dog. The technique was a lot like karate where you have to twist your hip to get enough power for your body and so that you can get the timing of the correction right. Most trainers do not give owners practice on a fence first. They just let owners make a lot of mistakes on the dog.