In fact I would gather that more back width and over all muscle has been gained from the simple, but brutally effective pull-up, than from all of those fancy machines you will find in most commercial gyms.
However as good as they can be I see people continually making the same result diminishing mistakes over and over. These mistakes are bad for one other reason, they open you up for serious injury as well and nothing stops training like an injury.
So without further delay, here are the most common mistakes:
Not warming up, I don’t know how many times I’ve seen this, someone will come right out of the locker room take a wide grip and start pounding away on the pull-ups, probably all the while thinking they are doing themselves a favor by warming up there back muscles for the coming workout. Unfortunately, this could get them injured, simply because a wide grip while beneficial does put stress on the shoulder joint and not warming up does not help matters at all.
Body momentum, I do not care what you call it, kicking with your legs or basically using any means possible to get your chin over the bar. It all adds up to the same thing, first you are not making the lats do the work, which is bad, but worse is the fact that all of this momentum and jerking is not good on the shoulder joint and will over time lead to an injury.
I know I mentioned the shoulder before, but it bears repeating, the shoulder is a very fragile muscle and should not be abused because once injured it takes a long time to heal and good luck in doing much training with a bad shoulder.
There is the guy I like to call, Mr. Half rep man, this guy loads up a dipping belt with a ton of weight, straps himself in for pull-ups and then all he does is basically half and quarter reps, and even for these he is jerking and using momentum to pull himself up. Not only is this dangerous, it is just stupid.
To me the pull-up is a wonderful exercise and should be treated as such, not only is it wonderful body weight only exercise, but it builds real world strength, that is strength that you can use outside of the gym as well as in. That being said I would like everyone to take it slow with pull-ups and chin-ups as well, only do what you can do, hey even one good and well executed pull-up is better than twenty sloppy ones.
Add one pull-up to that every week or every other week and soon you will be doing tons of them, but again, take care to avoid the mistakes mentioned above, and you will be well on your way building a stronger and wider back.