Clicker Training is the best possible training that is based on positive reinforcement out there.
All you need is a clicker and treats (I use high quality treats like cheese or chicken breast or meatballs).
You have to condition your dog on the clicker first. The dog needs to be able to connect the click to a reward. In the early puppy stages that is food and later on it can be a toy, or even a door that opens.
The conditioning and timing of the clicker is the essential part. If the dog isn't conditioned good enough he may not connect to the click so that is very very crucial.
There are different ways to condition. Some throw a handfull of food on the floor and everytime the dog eats a treat they click. Others give the treat out of their hand or throw a single treat on the floor.
What is important is that everytime the dog goes for the treat you click.
You throw the treat and as soon as the pup picks it up you click and you do that over and over and over again. Every day a couple of minutes and after the third or fourth day your puppy knows that "CLICK!" means "TREAT!".
Once your puppy is conditioned you can use the clicker to mar a behavior. Let's say your puppy sits down. That moment your puppy sits down you can click and you do that everytime your puppy sits down. Later on you can add a cue and at one point you won't need the clicker anymore. Or you use a treat to lure your puppy into the position and click. It doesn't take very long for dogs to understand what you want. Especially puppies learn rapidly fast.
After the puppy is conditioned the most important thing is timing, timing and more timing.
There is a lot of great videos on Youtube. I believe MaggieRoseLee has a bunch of very good links handy