i go in if i know that they have internally pipped at least 24 hours ago or so and nothing is happening some say you can wait a couple of days but i get scared and worry they will die in the shell, if they have internally pipped and you wait the 24 hours and nothing happens thats when i make a small hole in the large end you can see what is going on. if the chick seems really tired then you can take the end off. this is what i have done but some say not to help, so it is a personal call