I'm picking up TR (Roosevelt) in a couple weeks. He'll be 8 weeks by then. I want to get everyone's opinion on what type of collar to start off with because I want him to learn early and I want his learning experiences to be as positive as possible. Should I use a head collar or prong collar...or both? How early can I use either of them?

You should know that these are not equal tools to compare.

A prong collar allows you to communicate with your dog and issue information or corrections as needed, where as a halti, or any harness really, you can not do this.

Just yesterday I met a Husky and a woman new to town and we walked up the street with our dogs together and her Husky was limping, but only because she was pulling so hard in her no pull harness. Generally any information given to a harness will likely result in output the other direction, away from you.

Probably not with an 8 week old puppy, granted. But that said, if you practice proper leash etiquette and heeling early on, the better your dog will be. Puppies want to follow you. You can probably accomplish this with out either of your suggested tools at first.

4 months from now, different ball game.

I wouldn't use either one for an 8 week old puppy. Just get yourself a normal small puppy collar. For the record I HATE head collars. Dogs are not horses.

Most trainers will not recommend using a prong collar on dogs that are under 6 months anyway. At least from those that I know and have spoken to. Like Jen and Jeff said, a normal collar is what you should start out with when teaching a dog to walk on a leash and collar.

Yep.

Either would be overkill. They're intended to undo bad things, so work on preventing bad things