Most have no idea of what to look for,
follow MissPrissy's advice. Personally, I don't candle until day 24. When I do use an bator, I get my temp and humidity where is should be and leave it closed. I only add water if the humidity goes down or at day 18.
I love it when a hen hides her eggs and goes broody. All of a sudden, here she comes with her chicks. You see i have about 15 acres of mountian side fenced that my chickens free range on. Most of this has blackberrys and brush for them to hide in. I can't always tell which hen is where all the time. Last year I had 275 go broody at the same time, drove me crazy.