Hi,
You are in for a wonderful experience. Home hatching eggs is such a rewarding experience, almost spiritual, that you will never go back to buying live chicks again. The main think is temp, humidity and patients. The norm is 21 days for chicken eggs however, it may be shorter or longer due to many factors. Shorter's usually due to temp, longer is where most people run into the patients problem. *** It's 21 days from the day they "germinated" (for lack of a better word) not when they were layed or were put in the incubator. So, if they go over, don't get worried and start to open eggs. You will find almost ready to hatch chicks and feel really bad. Here's what I do,
1) DO NOT!!!!! Wash the eggs.
2) Set eggs at room temp pointy end down for at least 24hours.
3) Put them in the pre-warmed incubator, (on racks pointy end down) or on the screen gently on their side. Mark with a marker one side.
4) Keep and eye on the temp and humidity.
5) If you must candle them, (can't resist it) wait at least 8 days 'til you candle. HANDLE CAREFULLY. Don't shake 'em to see if you can hear anything inside.
6) Stop turning about 3 days prior to hatching.
7) Enjoy your chicks.
If you have any question, feel free to ask me.
Rick