Clicker training is a form of positive reinforcement (reward-based) training. You train your dog to associate the sound of the clicker with performing a desired behavior, such as sitting or lying down on command, and link that sound to a reward, i.e. treat. Dogs quickly learn to associate the clicker sound with the treat and therefore try to perform the action that gives them the treat.
Click the clicker and give your dog a treat right after clicking. Some dogs may find the sound startling, so if yours does, muffle the clicking sound with your hand. Continue to click the clicker and offer a treat until when you click the clicker, your dog looks up expectantly for the treat.
Click the clicker and vary the time between when you click and when your dog gets a treat. It can be just a few seconds to 10 seconds. Count silently and not out loud. This teaches your dog to expect a treat even if it doesn't come immediately after the click. Continue to train, varying the time until your dog is comfortable with the concept.
Click the clicker and then toss the treat next to your dog. He may act a little confused about the treat, so if he doesn't get it at first, show him the treat. Continue to click and treat by tossing the treat somewhere close by so that he understands you can put the treat in different places.
Combine clicking and treating in different places and during different intervals between the click and the treat. This will give you more flexibility in clicking and treating.
Pair the clicking and treating with a behavior. For example, if you want to teach "sit," click when you see your dog sitting. Give him a treat and then wait for him to figure out what he did to get to click. If it takes him a while, lure him into a sit, using a treat above his nose and bring it backward so he finally sits for it. Once he sits, click and treat. Continue to click and treat every time he sits.
Pair the action with a cue word or command. Following the sitting example, once your dog is happily sitting, use a cue word such as "sit," so you can associate the command with the action. It can take some timing to get it right, but the timing should be "sit," click and treat. Practice until he sits every time when you say the cue word.
Fade out the clicker, slowly removing it from the process. When you tell your dog to sit and he sits, don't click, but still give him a treat for such a good job. You may want to click sometimes and not click other times until he is sitting perfectly on command.
Fade out the treat. Like fading out the clicker, fading out the treat requires that you treat sometimes and not treat other times. Practice with both treats and no treats until your dog becomes reliable with the command and no treats.