Before you gather eggs for setting, make sure your hens have all of the essential nutrients readily available--I generally add riboflavin and vitamin E to mine's water before I gather eggs for setting because I know that's a deficiency in their feed. (
Riboflavin is the most common vitamin deficiency in poultry feed.)
Vitamin deficiencies. You can use a low-iron bird nutrition supplement if you don't know. They're available at Wal*mart and most pet stores. It's not absolutely vital, I once lost an entire clutch, so I'm careful.
When you gather eggs, you should find nice-looking ones, not big, not small, and no deformities of the shell. Store them in a cool, damp, clean place at between 45 and 70 Fahrenheit for less than fourteen days. (a week is ideal. Viability rapidly declines after ten days.) You can also check for fertility by cracking the eggs open and
looking for a blastoderm.
Temperature depends on the sort of incubator you're using. Still-air requires higher heat because the air isn't being moved around and there's uneven heat distribution. 100-101.5 is ideal. Forced air uses a lower range, between 98.5 and 100. Whatever you do, use two thermometers, calibrate using ice and boiling water, if you can, and never trust the thermometer they send you to be correctly calibrated. Too high of heat causes too fast of growth, too low of heat causes delayed growth.
Humidity should be between 40 and 50 for the first two and a half weeks of incubation, and between 60 and 80 for the last three days (
lockdown) Too high of humidity causes large, soft-bodied chicks and drowning in the shell, and mal-positions. Too low causes small chicks and "shrink wrapping" which is when a chick is restrained by the internal membrane, which has dried and now holds the chick in place so he cannot move to pip.
Judging humidity by air space
Internal pipping is when a chick breaks the inner membrane of the egg. External pipping (or simply "pipping" is when a chick breaks the shell. You may see movement and, if you hold the egg to your ear, hear peeping and tapping. You are not supposed to hold the egg to your ear because that involves opening the incubator which breaks the rules of lockdown. Note that this rule stops very, very few people.
Candling eggs.
Beginner's guide to incubation.