I agree with the above post. Training should begin straight away, and if your pup is slightly over-enthusiastic, this is even better! There's nothing quite like seeing your tiny puppy fling himself down on the carpet because you said "down!". As long as you don't expect him to hold a sit or down for more than a second or two (you need to have that treat ready to pop in his mouth as soon as his bum hits the floor!), he should be fine with some basic training.
Little and often is the key, because puppies get bored very easily, and can forget newly-learned commands if it's not repeated regularly. 5 minutes, several times a day, armed with some tasty treats, and he will likely throw himself into the exercise with the same zest and enthusiasm you have described
