People who have the goal to compete in Obedinece or Rally-O need to start with the very basic foundation work.  A dog can start as young as 9 weeks of age to five years of age or older.  Younger is always better!  Foundation includes learning about focus, stays, heeling, and lots more using props, toys and or food.  Clicker training can come in handy too!  Every dog learns differently so techniques are catered to each individual dog.