6-1/2 month old German Shepard

 What kind of trainer charges $600 and can't get a 6 month old pup under control? In general, I do suggest a trainer for that type of issue.

Maybe an Easy Walk harness would help you get some control? It will not allow him to lunge forward so easily.

I would invest in a consultation with a canine behaviorist. 

Until then, I would invest in a muzzle, a prong collar, and a leather leash as not to tear up your hand as badly.

I'll forgive your regretable choice of a team (I'm a Red Sox fan).

What sort of training did you do?  That's pretty darned pricey for the results you got.

I live with six german shepherds and in the past have done a fair amount of fostering.  The rescue I worked with often sent me the youngsters who needed to learn some manners and how to live with a family, canines and humans.

I use a long line to teach good leash manners.  If you are in a location where you can do this it's a great way to teach your dog to pay attention and focus on you.  With a new pupper, I don't take them out of the yard until I know that they pay complete and total attention to me on lead.  I teach "leave it" right away in conjuction with the long line, and I never stop talking to them when we are working.  When I take my own dogs out off lead it's funny to watch the ears swiveling around to make sure they don't miss anything I might say.  I never raise my voice and they sure don't want to miss me offerering a cookie!  The worst they ever hear from me is a rather obnoxious "eh" and they know that they did something I'm not thrilled with, and normally know exactly what it is they did "wrong"

My young boy was a reactive nut at that age.  Basically I stopped walking him regularly from 5mos - 10 months (he is 12 months now), until I could get him through that stage and get further in our training so as to have more control.  Just last night I walked all three of my bigdogs by myself, with their leashes all in my left hand, hanging loose.  A few months ago I never thought I'd be able to walk Nikon past other dogs in the city, let alone walk all three together on the sidewalk with no issues.  It takes a lot of time and consistency.  Nikon's probably was dogs, not really people, but we don't live in the country so on any given walk we might have to pass a dozen different dogs.  Months ago, he would bark, growl, hackle, and pull.  Now he just walks past, and maybe bristles if the other dog is acting reactive toward him, but he gives me eye contact when I ask for it, no longer pulls, and will stop and do obedience in front of the other dog if I ask for it.  A prong collar helped us a lot but I don't like to suggest that without knowing more about the dog.  Nikon was bred to be very active, strong-willed, with a lot of drive so a prong is the correct tool for him.  I only just recently started walking him regularly again.  It wasn't so much that I had to keep walking him and work through his reactivity, but it sort of went away indirectly because we turned our focus elsewhere, going to Schutzhund training and working a lot on drive development, games and rewards that motivate him to work with me and do what I want in order to get what he wants.  Now that we've added walks back into the routine, the reactivity is basically a non-issue even though I didn't exactly focus on that.  I just didn't have the control of my dog that I wanted, and couldn't control the environment (the other approaching dogs) enough to feel comfortable trying to train in that setting.

You said not to suggest training, but that's really what this dog needs - proper training of some kind.  If you cannot control him, I would stop walking him for now because until he understands what you want, he could become a liability and another dog giving our breed the bad rap.  You need to work on getting "on the same page" so that the dog respects you and has the desire to be with you as a team, not the dog walking the human.

Liesje

You said not to suggest training, but that's really what this dog needs - proper training of some kind.

That's the truth.  You can't judge all trainers by one experience.  I'm not saying the trainer was good or bad, there are many of both.  Training a dog is all about consistency and not letting the dog get into a situation YOU can't control.  It's not an insurmountable problem if you are willing to devote some time training.  Patricia McConnell has a booklet called "Feisty Fido".   It's not expensive and has good advice.  A good professional can help you get started by showing you the tools and explaining the theory.  It might be a good idea to find another trainer but only you can really train the dog if it's to be a permanent change.  You can do it and your arm and shoulder will thank you forever. lol 

http://www.apdt.com/  You can search for a trainer in your area here.

I can't believe I'm giving advice to a Yankees fan lol ('nuther loyal member of Red Sox Nation that I am)...

Anyway, if you have a large, powerful pup then ONGOING training with a GOOD trainer is a must.  Until you get the dog trained, you can try walking him in a Halti head halter (easier for newbies to use), or a Gentle Leader (that one has a video you can buy that shows you how to use it).  But, before you put it on, acclimate him to think it's a really good thing!!!!  So let him smell it while he eats roast beef bits, then feed him some meat through the opening, then put the nose loop on and off while feeding, then feed as you put it on and hook it up.  Take it right off.  Next time, hook it up (still feeding a few treats) and walk a few steps - keep luring him on by feeding any time he decides he "doesn't like" the halter.  Next step is to make him do a few more steps before he is rewarded.  Soon, you will be doing more and more steps with fewer and fewer bits of food.  But, keep a stash ready.  When you see something coming that ordinarily excites him, back away BEFORE he reacts and feed him for doing a nice sit.  If he gets wound up, or won't take food, go farther away from whatever he is concerned about and try again.

Yankeesfan

Are there any suggestions on how to correct this problem.

I am sorry to say it, as I know you don't want to hear it but.... training is the only way to correct this problem. 

Train, train, train.  You simply CANNOT own a dog like a GSD and NOT train him, frankly.  ALL dogs need training, but especially smart, powerful dogs, like Shepherds.  If you are determined not to train him, you really do need to rehome him to someone who will.  I am not suggesting go to an expensive trainer, but learn how to train the dog yourself. 

I agree with Liesje - abandon walks for now, until you have the dog under control.... or only walk him in quiet areas at quiet times of day, and DEFINITELY research the tools that will help you to restrain him in the meantime.  If you are concerned about what he might do if you are unable to hold him, then PLEASE train him to accept a muzzle.  (Oh dear - that T word again!  Sorry!)  Get a basket muzzle and stick a smelly treat in the end for him to stick his nose in.  Work up to fastening it, and then letting him wear it for walks.  (That is "training" - it doesn't always have to cost hundreds of $$.)

It would be useful if you could expand on exactly what the trainer did that cost you $600, and what you have done to train the dog by yourself, so far.

Also, how much exercise (mental and physical) does this dog get each day?