I don't know how you do it but this is basically the system I am now using.
Build recall - my puppies had the recall whistle from the very first plate of slop that I gave them; the bowl is held down and the whistle blown - the pups are already coming to hand. This is a very important element - the come tohand bit on every recall and something I insist on 95% of the time even on an older dog (sometimes I recast before they are back) - after all a retrieve is just a recall with a mouthfull.
Build the desire to retrieve - i start by forgetting all about steadiness and let the dog run in for every dummy. Every thing that is ever picked up and brought to me gets effusive praise (quite hard when it is you socks or shoes or glasses for the umpteenth time). The dog is never ever wrong to bring me something. Also much praise and chest rubbing and firm stroking before ever taking the item.
I introduce the stop whistle and throw a dummy as a reward. Because the dog wants the dummy so much - because of the job in the step above it will stop and spin around to look at me. One can increase the length of time it has stopped before throwing, adding a hand signal to be able to hold the dog as the dummy is thrown and release it on command.
Taking a line. Choose a path through low vegetation - dogs tend to run defined paths rather than crash through undergrowth. Drop a dummy so the dog sees it and walk on - turn and set the dog up for a blind retrieve and use your body and arms and hand to create a guide, send it back; increase the distance. Once you think the dog has got the idea you can drop a dummy unseen and send it for that (same path idea, same path even) Just make sure you reduce the distance to the 'beginner level' however. Always always use the same build up and hand signal and language. It is a ritual. The outcome is the same - always for the dog; at the end of the run in the direction you have pointed is a retrieve. If the dog goes wrong ie veers off have an 'I don't like that ' noise (I use 'ah ah ah' If you use the stop whistle you will find the dog will quickly anticipate this and become sticky.
Next step is to walk a dog leg so the dog is now not going back along the path it has just taken. Then on to 'seen retrieves' that have been thrown. Whilst there is an argument the dog should mark it and not need any guidance in the early days i like to go through the same ritual. It helps the dog understand it is in retrieving mode and not in hunting mode. If it miss marks don't let it hunt but pick the dummy yourself and try again. When throwing 'marked retrieves' make sure the dog actually has something to mark against - a tree something otherwise your are wanting it to measure trajectory not mark a fall relative to a fixed point, something it can navigate to and around. Teaching trajectory appreciation is easy - throw a dummy and let the dog run to it as it falls - I have yet to see a dog end up in the wrong place.
apologies about swapping between first and third person - not time now to modify it :-) off to the vet with a dog with hot ears.