Letting the puppy drag the leash around is a good idea. Make sure that you supervise him closely so that he isn't getting hung up on anything with it, and that he isn't chewing it into sections. The thin nylon leashes are cheap and light weight and perfect for this task. You do not want to attach a leash that is too heavy. That will defeat the purpose and confuse and frustrate your puppy. The leashes they sell for cats and small breeds like Chihuahuas are just about perfect for an 8 week old puppy.
As for teaching puppy to walk on leash? Hold the end of the leash in your right hand, have puppy at you left side. Bend over at the waist and hold a squeaky toy (of course, you should be squeaking it!), a tasty treat (or something else that puppy likes and wants) in your left hand, about 3-4 inches in front of his nose. When puppy reaches for it, move it forward just out of his reach, luring him into walking forward. Praise him like crazy in a high, excited voice. Do this for maybe 10 seconds at a time, off and on throughout the day.
Your puppy is just a baby. Don't expect too much, too soon. And I would not think about working with him in terms of "dominating" him. Everything right now should be super fun, and super positive. There is no room for "domination". Your puppy will look to you as a leader because you are fair and consistent, not because you can dominate him.
Have fun! I envy you having a puppy!