Labs are generally great dogs, intelligent and eager to please, but clownish. The trick is to make them think that what you want them to do is really what they want to do. Tell your friend not to drag the pup, it can be harmful. Also, use food treats and lots of praise for the good things the pup does, and lots of distractions (food, praise or toys) for the inappropriate behavior. And experiment with toys, till your friend finds one the pup really likes. I never worried too much about leash biting at first, knowing the dog would eventually be distracted by other things. But by six months I would not want the dog gnawing on a leash too much longer. Best advice is already given, get Ed's tapes. But also check out his questions and answers on his web site.
Best of luck to your friend.

Ah, the happy-go-lucky lab. My parent's lab exhibited the exact same behaviour, with the added behavior of barking whenever she decided she'd had enough of being in the dog run -- my parents would come running to cater to her, erg.

I came home got chewed on, slobbered on and decided that I'd had enough. I put on a choke and a leash and wham! she hit the ground and wouldn't move. Tried coaxing. No go. Treats. Uh-uh. Took it off -- bounce! bounce! I thought about it for a moment and then locked her up in one of the spare runs and instructed the rest of the family not to even go near her and to ignore all fuss coming out of there.

The programme was simple. If I went in to feed her or pick up any mess, I completely ignored her. The only time she got attention was in the short sessions (I had 4 5-10 minute sessions in the day) and the only thing she got attention for was willing obedience. The first couple of lessons were just learning to accept the collar and leash and to heel at my side (nothing strict). I teased her with a treat to begin with to break down resistance to being on a leash. If she didn't respond, I just cut off the lesson, put her away and came back in a couple of hours. By the last lesson that evening, there was a complete turn around -- when I said heel, she'd plaster herself to my left knee, look up and start licking her chops and would follow through in all pace changes and turns. She took subsequent lessons and corrections very well (so much for a soft dog!) and generalised lessons very quickly.

As for barking, oh she did bark...barked herself clean hoarse before she realised it wouldn't help and stopped. I made it a point never, ever to approach the run when she was barking. If she saw me and started, I just turned around and walked away until she shut up, at which point I'd turn back. She got the hint quickly.

It took 3 days for her to get rid of the habits that so annoyed me to begin with. From then on, it was just a question of working on obedience, proofing it, building on it. Incidentally, my parents made me stop isolating her after 2 days -- they felt so sorry for her. They did have to admit that she quickly became a much easier dog to live with: still very happy and energetic, but much more polite and nicer to have around.

Considering that this puppy is just 5 months old (are you sure? 60 lbs is kinda heavy), isolation may be a bit drastic but crating the dog or defining a 'place' that they're expected to stay at is a good idea. Apart from everything else, it's a good start to interacting with your dog on your terms, not the ones it wishes. Tell your friend to control his dog's environment, find a consistent obedience programme and follow it. It's the best way. I'd recommend a book I've found helpful in this regard, but I don't know how acceptable that is here.

Paul,

The reason you were getting no help from some but the same advice over and over is because of something you said. You said your friend

"thought maybe if he dragged him enough the dog would get tired of it and would give in and get up and walk"

When I hear something like that I don't even know where to start. This trainer is so off base that he really needs help. Like I said, more help than we can provide here and now.
I would hate for your friend use a few tricks that he learned on this board to get the dog "up and going" and then fail to learn all that he really needs to. Again, this video is REALLY in order here, IMO.

I've never watched the video, but I do agree that the friend needs to start using positive motivation on this pup. I also agree that this friend is SO far off base, that advice from an internet bulletin board (as great as this board is) is inadequate. Your friend needs help in a big bad way, and needs to be adult enough to see the error of his ways and change them, and not be too defensive to be open to learning.

Another concern I have is the pup's growth. I hope this pup is on a "large breed puppy" food, not regular puppy chow type food. Growing too quickly is so bad for the larger, more active breeds. It leads to structural problems later on that will affect the dog physically.

I'll tell him to hire a pro and get Ed's tape.

Good man! And don't forget to tell him about the food/growth issue!