Lead training

A flat collar, one that does not choke, is required to prevent unintentional constriction or pulling. If you expect your dog to try to slip out of his collar, you may "back it up" with a choke collar to prevent his slipping free.
One word of caution: you should never need to apply enough tension to cause your dog to back up and slip his flat collar. Whenever pulling occurs, just say "no", immediately give slack into the lead (without stepping forward) and follow with "good boy".

Tension on the collar must be released instantly. If pulling continues, you may need to pull your dog back just one inch, as you say "no", just enough to gain the slack necessary to give it back to him, while praising.
This technique and a practice exercise will be covered in detail in the trouble shooting section.

Here's something arbitrary, and a brief aside you may appreciate. While instructing a "burly truck driver type" (no offense meant to either burly men, truck drivers, lady truck drivers, burly lady truck drivers, trucks, any others, or any breeds of dogs), regarding praising his terribly out of control Cocker Spaniel while training with me, told me flat out, that he could not "do that" (meaning praising his pet as I requested).
My chin hit the floor, my heart lodged in my throat, my temples began to throb, my hands began to shake, and I knew I would be leaving this appointment suddenly, and maybe not in the same state of health with which I had begun this session. It had happened once before, that a "macho" student of mine refused to follow directions at the onset of our lesson.

His issue was that my approach to handling his out of control Great Dane was not in keeping with appropriate handling techniques, he "knew better", as he had "experience" with police dogs, and he simply was "not going to do that".

I can only presume what he meant by "do that" was show respect and common courtesy to his charge. On that occasion, I was fortunate (rather, his Great Dane was fortunate) that his wife was observing the lesson and I was able to obtain permission to begin the lesson over again, using the wife as primary handler. Continuing with the original aside... As I sadly began to collect my equipment, I asked, "why can you not speak to your pet as I request?"
He lowered his eyes, and mumbled that he just cannot talk to his dog "like that".
In a last ditch effort I asked, "well, how do you talk to your dog?" He said that he had a very special relationship with his critter, and he always talks to her in a particularly loving manner.
"Show me how you do talk to her". At this point, he began a litany of cooing and prose that still cause me to wretch with laughter! I realized then, my concern was for naught, and my efforts would be valued and appreciated. .