How I got there from barely being able to hang using neuroscience
It took me a year. A year to go from hanging from a bar and my grip failing in ten seconds...
...to one single, clean pull up. This means no swinging, no kipping, no half-reps; just start full hang and slowly raise chin above bar.
Here's what I would stick to if I had to do it again.
My source material (buy here): Convict Conditioning -By Paul Wade
TIME UNDER TENSION.
Forget the details, the more you work a muscle group, the faster it learns.
10 x slow, controlled lower progression reps is better than 1 x fight to get over bar.
Always!
Go backwards to progress faster.
You will stay more motivated performing good clean reps than fighting for one good pull up.
If you can't do 3 x 25 reps of the progression you are at. Do not move on.
GET A GRIP
Beginners, ignore all of the options.
Complete the basics, then have a play with variants.
Just stick with a basic protocol and get good.
Dead Hang EVERY day. It...
Strengthens grip.
Extends spine beautifully.
Re-aligns shoulder girdle and fights bad posture.
Strengthens the rotator cuff muscle group
Assistance bands are BANNED!
Do not use a support which presses up from beneath (feet, knees etc).
The body has to learn at a neuro-muscular level to PULL.
SEE PRINCIPLE 2.
Skills take time.
Be prepared to rinse and repeat..a lot.
Hebb's law "cells which fire together, wire together"
Your first month or so is simply skill learning (no muscle gain) as you'll be filling up unused capacity in your soft tissues etc.
In short - tortoise beats hare!
LOOK AFTER THE JOINTS AND THE MUSCLES WILL LOOK AFTER THEMSELVES - UNLOCK THOSE HIPS