Dogs that are as young as four to six weeks old can begin to learn various things. You should start by training them with their name. They should learn to respond to their name. This will happen quickly and naturally if you use their name when talking to them on a regular basis. Once this has been accomplished, dog training can keep going.
Dog training is a long term process. It takes a long time for a dog to learn various types of tricks. The best way to teach them is through repetition. While you can reward dogs for doing the right thing, you should realize that that reward does not always have to be a treat. You can give them affection and encouraging words too.