I helped a chick the other day and it's still alive, although it was really weak at first. It had pipped almost all the way around but was having trouble finishing the job (it had been pipping for almost a day).
I had a cup of warm, but not hot, water ready. Then I took the egg out of the incubator and with my finger, dipped in the water, I moistened the membrane that I could see through the crack. After it was thoroughly moist, but not soaking wet, I pulled up (just a tiny bit) on the top half of the shell where it was already pipped. This loosened things just a bit to give the chick more leverage for the next time it pushed on the shell. I moistened the membrane again and replaced the egg in the incubator. It was only a short while before the chick had finished getting out.
It was super weak and I thought it would die. It didn't help that the other chicks decided to come over to it and peck at it so I moved the weak chick to a corner of the bator and surrounded it with some of the unhatched eggs. I expected to see a dead chick in the morning but it was still alive. It's feathers were very sticky, rather than fluffy, so I removed all of the other chicks and left it in there by itself. Later on I put it in the brooder with the rest and it's doing alright.