Dexter is 9 weeks old and we have started obedience training almost right away.
I believe that there is no such thing as too early to start basic obedience training with a dog. As long as a puppy can be excited with food or toy, it can be trained basic obedience skills. Sit, Come, Down, Place … are all mandatory and essential skills every dog needs to have. The earlier a puppy learns these, the better your relationship and bond will be.
The key is to use only positive reinforcement in your training. There should be no negative reinforcement in early stages, as you are trying to build a bond and connection with the young dog. Harsh and negative correction will only hinder the process. Patience, repetition and lots of treats will get the job done quickly and with lots of fun.
In addition to learning a skill, a puppy will also drain their mental and physical energy while it is learning new skills and thus will be calmer and more relaxed at home.
DO NOT be stingy with your praise and treats. Puppy needs to receive a treat as soon as he performed a requested skill. This is something excellent dog trainers are amazing at. Also, use treats that are easily broken down into small pieces and can be swallowed by the puppy as fast as possible. You do not want him concentrating on chewing, but on doing the task. It is more about the flavor and the act of receiving food for the dog and not about the amount it got.
I use turkey hotdogs, uncooked, and cut into tiny pieces. They are cheap, dogs love them and are easy to cut in to small chunks.
Teach/play with your puppy for 5-15 minutes at a time and always end on a good note. If you see the dog is getting tired and losing concentration, have him do an easy task, give lots of praise and let him rest.
The more you do this with your dog, the better will be your bond and you will have a happy and stable dog.
Here is a video of Dexter and I working on his come and sit skills. It took me 2 days to get the results in the video.