STEP 1: LURE THE DOG
Position yourself in front of the dog put treats in front of his nose and take a few steps backward. The moment dog makes the step towards you press click. After click wait for a second for him to come to you and give him the reward. Repeat this step until you can reliably get your dog to follow you then proceed to step 2.
STEP 2: ADD VOCAL CUE
Pick your cue wisely, the best cue would be something you don't say often in general conversation. It could be "Fido come". Make sure you say it in a happy voice. Once you could bet some money your dog will follow you and the treats you repeat step 1 but first you say your cue ( "Fido come").
STEP 3: REMOVE LURE
Make sure there are no distractions for your dog. For example, your dog isn't sniffing or doing something else. He is mainly focused on you. Set some small distance between 2 of you a meter or so and say your cue. The moment dog looks at you or takes a step towards you click and reward him. Encourage him and produce a lot of happy sounds so it will be interesting for him to come to you. If it doesn't work go back and repeat step 2 a few more times
STEP 4: ADD DISTANCE
Once you can reliably get him to come to you from a meter away put some more distance between 2 of you. Don't go too wild, and take small steps. So for example, if your dog is coming to you from 1 meter away try to get him to come to you from 1.5-2 meters away don't go directly to 10 meters. Each task you put in front of your dog you want him to complete successfully, that way your cue will still work and you will both be happy.
STEP 5: ADD DISTRACTIONS
Once you can get him to come to you from 10 meters away go back to 1 meter and add some distraction. You can put a less interesting treat than the ones he usually gets near him in the opposite direction of you, and tell him a cue to come. The way you do it in practice is you take his regular food he eats every day and put it near him but in a way, he cannot reach it. Then you walk 1 meter away in opposite direction and tell him a cue for which you reward him with a delicious treat like a small piece of ham. The moment he takes interest in you or makes a step towards you click and reward him. Again the most important part is for him to be and feel successful and pleasant. If he keeps more interest in a food on the floor than you, use a leash and gently guide him towards you.
Never use your cue to come when something unpleasant for your dog is about to happen, and never punish your dog. Especially after he comes to you after telling cue. What will happen if you are mad because the dog chewed your shoe and you decide to call him and punish him? The dog will think you are punishing him for coming to you after the cue. In other words, you will loose your cue. The way dogs perceive it is that everything (a reward or punishment) is coming because something they have done a few seconds ago. So if he chews your shoe while you are at work, you come home and call him. He comes and you punish him. He will have no idea it is because of the stuff he did 4 hours ago. He will think it is because of something he did a few seconds ago and that is coming to you. Because it is really important that come cue works, don't use it when something unpleasant is about to happen after it. For example, if your dog doesn't like brushing or taking a bath, you must not use the cue to come before making him take a bath. Your dog will understand that as punishment for coming. They are simple beings and they will think ok, I come and this cue is for something unpleasant for me. I shouldn't come when my trainer is using a cue.