Hi Karen, there are no hard rules as to how much retrieving you do, little and often are usually better than one long session, as it allows the dog time to absorb what it has been doing between sessions, and it allows you to see what the dog has absorbed and learnt and then adjust the next session accordingly. A word of warning, ( again) just because the dog does something on numerous occasions does not necessarily mean its learnt the instruction to the behaviour, only when the dog does the right behaviour to your instruction in a `variety' of environments can you be sure that the association has been established.

Its very important to remember, that to a dog, especially a young dog, retrieving is a game! The onus is on you to maintain this perception, it must remain fun to do and you have to add variety, allowing the dog to move forward and feel good about its expanding achievements, whilst maintaining a competent ability. Never let the dog dwell on failure, if you go to far or too fast with training and you see the dog is not likely to succeed, stop the dog ( you have all trained the stop!) and do something basic which you can reward, in retrieving terms, even allowing the dog to see you go out and pick the retrieve yourself, whilst in the stop, can build respect from the dog towards you, in fact when retriever training at least one retrieve should not be given to the dog at each session, this adds value to the retrieve and improves steadiness.

Hi Penny, As I have mentioned before, retrieving is a game, first the game has to be learned. At this point I would just mention that dummies are not toys, they are items of yours that are highly valued. Part of the transition from a game to work involves this understanding and separation. A good natural retriever brings you IT's toys from which the game of retrieving begins. i.e. Handler takes toy and makes it move, requiring puppy to chase it, capture it ( kill it)
and bring it back to show what a good hunter it has been. Handler quiz's the puppy to what it has, puppy drops toy, handler gives puppy reward and makes it feel good and therefore is happy to do it again. The game has been established. In order for the game to continue the dog must get use to sharing its possessions whilst being confident that it will get them back, and at the same time bringing things ( non-toys) to the handler is always a worthwhile thing to do. Only when the puppy has this understanding would I consider starting with a dummy, as that's when rules start being introduced to the `game', and they must be mature enough to except them.
In your case I would go back to using a tennis ball or similar, play the game, after the first few times where you can fetch the ball if the pup does not bring it back, start, stop playing the game when the dog does not bring it in close, and walk away, from the pups point of view the game is not much fun on its own, and you may quickly find that it soon comes looking for you, and with any luck will be carrying the ball, in which case the game can continue, thus a valuable lesson has been learnt.
Peter