I use the backs, necks, wings, gizzard, heart, and feet. If I pluck the chicken instead of skinning it, I put a lot of skin in there as well. I throw in some peppercorns, a carrot, celery, an onion, and usually basil, oregano, parsley and chives, depending in what is available in the garden. My wife does not want me to use garlic, but that is another option. All that plus as much water as I can fit in goes in the crockpot for maybe 10 hours, set on low. You can cook it in a stock pot if you wish. I usually do 2 or 3 batches at a time. With the first ones, I put then through a strainer and put the liquid in the refrigerator. When I take them out, the fat has firmed up on top and can be taken off. A lot of times that liquid is more gelatin than liquid when cold, but not always. That depends a lot on the age of the chicken you are processing, both from size and maturity level. The older ones have more "connective tissue".
I pick the meat out and use that as cooked chicken meat. Chicken tacos, chicken salad, in casseroles, however you would use cooked chicken.
I then finish separating the fat from the liquid. I warm up the stuff from the refrigerator since the fat will separate better if it is warm, and use one of those fat separators where you plug the spout, let the fat rise to the top, then unplug the spout and pour the good stuff out from under the floating fat.
I put a regular strainer over a pot and put four or five layers of cheese cloth over that to catch the big bits and strain it in a big pot. Bring that to a boil, fill the pints with 1" head space, and process at 11 pounds for 20 minutes. I use 11 pounds instead of 10 due to the elevation adjustment.
We all have different ways of doing it, but this is my basic procedure. I usually get about 5-1/2 pints per batch, but that depends on the size of your crock pot. My last canning was 16 pints from 3 batches.