Once in a while I pick up one of those over-cooked whole chickens at the super market if they are on sale.

All meat is removed as soon as I get home and separated into dark and white (breast) and stored in separate containers in the fridge.

The rest, all the bones, skin, neck, tail, etc. goes into a large boiling pot. Also dump the juice at the bottom of the plastic bag into the mix.

Here is a recipe I stole from a cooking website. I do not recomend the slow cooker method, but that is what this author seems to use. You don't have to have every ingrediants mentioned, but it helps:

Essential Chicken Stock

Makes 2-1/2 quarts
 
Having a good stock in your kitchen arsenal is essential for full-flavored sauces and soups. Feel free to add your own touches such as mushroom stems or additional herbs and spices. While canned stock will do in a pinch, homemade ranks head and shoulders above it in richness and flavor. I always have a container of chicken bones in my freezer. When I have enough bones, I'll start up a batch of this stock.

I cool stock in a sink filled with ice water (this does the job quickly), then store the stock overnight in the refrigerator. This makes it easier to remove the fat that rises to the top and hardens.

Store in the refrigerator, covered, for up to 3 days, or freeze for up to 3 months.
                 
to 3 to 4 pounds chicken bones (wings, carcasses, and necks) add:

?                 1 large Spanish onion, roughly chopped
?                2 medium carrots, peeled and roughly chopped
?                 1 celery stalk, roughly chopped
?                 1 thyme sprig
?                 5 flat-leaf parsley sprigs
?                 1 bay leaf
0                 1 whole clove
?                 6 whole black peppercorns (about 1/4 teaspoon)
                 
Approximately 3 quarts water

1. Preheat a 6-1/2 quart slow cooker to High.

2. Place the bones in the slow cooker insert and add the onion, carrots, celery, thyme, parsley, bay leaf, clove, and peppercorns. Cover the bones and vegetables with water only to the top of the bones. (If you add too much water, the flavor will be diluted.) Cover and cook on High for 6 to 8 hours. You know your stock is done when it has a deep yellowish color and tastes very rich in poultry flavor.

3. Strain the stock into a clean container and discard the bones and vegetables. Cool the stock completely, and ladle off the fat from the top of the stock.

4. Portion the stock into storage containers.