I treat it like building anything, once you have a solid foundation you can build on it, but always go back over the basics.
He will tell you when your ready to move on... once they get what you've been working on they will try you becasue their bored.
I still have my Labs, even a teenage lab, heel before I release her to eat. And sometimes I even have her heel halfway into a meal.
However, when I do start anything new I make it fun and then start to refine it from there.
Enjoy it...it's a learning process for us too.