For the sake of the video, I did several recalls in a short period of time. In real life, I would suggest no more than one recall every 5 - 10 minutes on your walk because otherwise your dog becomes too interested in recalls and stays at your side the entire time.
I use "come" for my recalls, but you can choose another word. "Front" and "here" are good options. Do not pick a word that flies out of your mouth all of the time. Do not use a word that you have already trained your dog to ignore most of the time. This is not a recall I use casually or around the house. When I am being casual, I use something else.
My dogs know that "come" is not optional, but it is also highly rewarded. I always pay my hounds for good recalls for their entire lives.
Obviously in the video above, the demo dog (Seven) is already trained and promptly responds to me each time. In real life, you will likely be ignored at first and this is exactly why you have them on leash. Gently tug and turn your dog around. Often he will start to chase when he sees you running backwards. Each time you practice a recall, always give your dog two seconds to respond. I often have people in my classes that get in a bad habit of jerking their dog each time they call. In those cases, we have no idea if the dog was going to respond or not, so give your dog a chance.
If you are generous in your rewards and your dog enjoys eating, this is a great way to teach an emergency recall for the day when your gate is left open or your dog slips his collar. If he has been paid handsomely for past efforts, there is no reason for him not to come bounding back to you.
Don't forget to touch the collar!