Everything you want to teach your dog, every new task should be built out of several small exercises and trained separately. They should only be put (partially) together when the dog is solid of the individual tasks.
Every small exercise though needs – and this counts for any kind of dog training – a special system of repetition, because this increases the conductivity in the brain.
In my last blog I wrote about Conditioning. If the dog shows wanted behavior he (should) get a reward each and every time = Positive Reinforcement. The dog is an opportunist, and learns that his success coincides with your desires until he reflexively and habitually does what you ask for.