Today me and Kate (other friend named Kate!) made homemade apple sauce!! Kate is a canning professional and this was my "introduction"to the wide world of food preservation.
FIRST, get a lot of apples. Wash with a produce wash if available. The main thing about canning is cleanliness. Anything you can do to keep things sanitary is good.
NEXT, peel and core your apples. We had this fancy apple peeler from Pampered Chef. It didn't always work though ... but it sure helps with hand cramping from the regular peeler.
Put your apple pieces in a big pot with about 2 inches of water. Cook until soft (about 20 minutes or so.)
Drain your apples and puree in a food processor (things are starting to shape up --- and smell AMAZING.)
Re-heat your pureed applesauce in a pot until it gets to 200 degrees F. In the meantime, boil your lids and gather your jars. The jars should be freshly washed and sanitized with heat in the dishwasher.
Fill your jars with a funnel to about the bottom of the lid (do not over-fill.) Return them to a boiling water bath with the lids on and cook another 20 minutes to seal and pressurize.
Allow jars to cool and you will hear them "popping" as they contract and seal up nice and good :)
NOTE: You can certainly add sugar, cinnamon ... what have you. We kept them simple since the apple variety was pretty sweet on its own.