How to tell if an egg is fertile

[ChickenGirl555]

Ideally 40-50F is given as a good temperature to keep them at and you can keep the humidity in by putting the eggs in a sealed plastic bag. I hatch quail and in the summer there's no way there's anywhere cool enough to store eggs so I try to use them as fresh as possible and it might mean the chicks arrive a day early.

Thanks for all of your help! I might post another thread for extra questions or to see what others do. But thanks for everything!