A Pomeranian Puppy isn't born automatically accustomed to a leash and collar. For some, it's a real shock to find something suddenly hanging off his neck, and an even bigger shock when that thing is pulled up short, stopping him in his tracks. Give him a few days to get used the idea first.
Start by attaching a string about two feet in length to his collar. For a small pup, this should be long enough to trail behind him, and for him to play with, but not heavy enough to be really noticeable. Let the Pomeranian puppy play and drag it around until he ignores it completely. At this point, exchange it for a heavier rope, and repeat.
Once the puppy is ignoring the rope too, put the actual leash on, and let him get used to that too. Once he's ignoring the leash too, start to step on it once in a while, to stop the Pomeranian Puppy from moving forward, and then pull on it to compel him in a different direction than he wants to go. He might fight it, or he might go out of curiosity.
The Teacup Pomeranian Fights The Leash
Some Pomeranian Puppies just don't appreciate being led around. If he starts to fight the leash, and I mean full body twisting, yanking, biting at the leash, not just resisting the pull. Once he starts fighting, don't let go of the leash, and don't continue to pull on it, yet.
Teach Him Not To Pull On The Leash
My favorite method for teaching a puppy not to pull on the leash is the "tree" method. Become an immovable object until your pup ceases to balk at the leash and allows a slack to develop. A standard nylon buckle collar and a six-foot leash is all you will need for this simple training exercise.
Remember to keep training sessions both short and positive, so training stays fun for you and your puppy. Puppies have notoriously short attention spans, so five minutes at a time, several times a day will help cement things firmly in your puppy's mind without him growing to resent the time take away from play. Take your time and be patience and persistence will get you there.