find a nice long alley/corridor that your dog cant get out of, throw a dummy/toy down to the other end of the corridor/alley and stand about 3/4 of the way the other end, your dog should fetch the dummy and try to trot past you. walk backwards slowly calling your dog and when it tries to pass, bend down, stop it passing and praise it, not taking the dummy. still move backwards and when you reach the end, put your hand to the dogs mouth and tell it to drop it, if your dog does, praise it and give it a treat. hope this helps, if you have any trouble pm me and i'll try to help some more.