Wouldn't using a prong "dead" put all the pressure on the front prongs b/c if the dog does pull against it, it won't evenly tighten, thus defeating its purpose? Granted, I've never tried using a prong on the dead link, but if you don't want the collar to tighten, I don't think the prong is the collar to use.
Acurajane, I wouldn't use a prong on a pup just yet. Personally, I prefer to train heeling OFF leash, either indoors in a large room or outdoors in a fenced space or dog run. I mark and reward the dog any time it returns to me, and as it follows me around in order to develop a "heeling" type of behavior. That way, I don't have to rely on any type of collar to get my dog to heel. "Heel" should mean the dog is in position on your left, regardless of whether you are stopped or in motion, fast or slow, turning or straight.
Prongs are safer than a choke, though. A choke puts all the pressure in one spot and tightens indefinitely. A prong IS a martingale and can only tighten so far and it puts an even amount of pressure around the entire neck (the more prongs the better, I never want less than 10 prong links).
If you want to use a training collar other than a prong, I would try an Easy Walk harness.