I know some ppl say not to help hatch but I did with mine and they are fine now. I am glad I did. If it has been over 8 hours and they have been pipping and zipping for that long give them an extra boost. It is okay to lift the top of the incubator for that long. Go ahead and take the baby chick out. If it is still alive, get a water droper and sugar water, pedealyte howerever you spell that and drop tiny bits on its beak and do this a few times an hour. Put it in small box with a light on it and keep it warm. I had to do this with one of mine. It laid there for a day and a half and finally I got it to perk up.
As far as the ones hatching peel little bits of the shell off at a time. Very gently. Make sure you have some warm water and a coton ball. carefully pull back the membrane. Wet it a little as you go. If you start to see blood stop and put it back in the incubator and let it sit for a little while. Then try again. Keep doing this little by little. Eventually it may be able to hatch itself or you may be able to finish it. This is a very long process. I would help though. I would have more alive if I would have helped more. But thank goodness I helped some and now have seven happy, healthy fluffy butts.
There are very various opinions on this but as for me I considered it life and death and I am very thankful I helped.