There's nothing better in soup than homemade stock. Making your own stock is a great way to stretch a buck; you're using food that you've already bought and doesn't require any additional ingredients besides water and herbs. It's also delicious and easy!
Whenever I roast a chicken, or even part of a chicken that's bone in, I stick the bones, fat, extra juices from the roasting pan, skin, and any other non edibles into a plastic container and stick them into the freezer until I feel like making stock. Also, as I'm preparing vegetables, I always save the root and tip ends of onions I'm chopping, the tops of carrots, and the stems of mushrooms. You could really add any extra vegetable bits you want. I also store these in the freezer until I get around to making my stock.
On stock making day, I take out those containers and dump them into my big pasta pot. If you have a big stock pot, I'm sure that's fine too. I don't have one. This stock is missing carrots. I think stock is way better when you've got some carrot tops to add in, but husband isn't a huge carrot fan so we haven't had any lately. I think you have to have onions though. They add a lot to the stock. You'll want the bones of at least half of a chicken or more. I also added in some beef fat from a roast we had. Repeat after me, "Fat is flavor." I'm sorry if you're concerned about your triglycerides, stock is not the place to skimp on the fat. You're adding so much water into the other ingredients that it's really not doing that much damage.
I also like to add some fresh rosemary and bay leaves to my stock. There's probably some rosemary already in the containers because I usually add some to my roasted chicken, but adding fresh wont hurt anything. You can see I'm using the bottom of the bay leaf container here.
How much salt should I add, you might ask. NONE!!! You can add your salt when you make your soup. This allows you to control how salty each soup is. I use dried black beans a lot when I'm making soup, and they will not cook and soften properly if there's salt in the liquid.
Fill your pot up with water leaving about 1/2 inch of room at the top so it doesn't boil over. Cover. Bring your mixture to a boil, then turn down to medium high so that it will continue to bubble, but not boil over. I usually cook my stock for about 2 hours, but I was extremely exhausted when I made this and only let it go for one hour.
Use a slotted spoon to remove the big chunks from the pot and throw these away. I'm sure you've got a nice strainer in your kitchen, but all I have is a colander. I set my colander over my plastic container. I like to use those plastic containers from take out soup because if they crack in the freezer I'm not out any cash. Very carefully, ladle your stock into your strainer. IT'S HOT.
Let the stock drain into your containers leaving behind any chunks you missed before.
Even though I only let my stock cook for an hour, I still got an amazingly rick broth. Look at that awesome color!
Make sure you leave a centimeter or so of space at the top of your containers. The stock will expand in the freezer. You'll want to wipe off the bottoms of your containers because there's probably some condensation or excess stock on the bottom that you wont want in your freezer.
I can tell you for sure that the stock is good for at least 3 months in your freezer, but I've never kept any for longer than that. It makes for some amazing soups, stews, and chilies. I've also made seafood stock before from the tails of some shrimp I had saved. You can really be very creative with your stock.
*Update* since I've written this post I've saved up another batch of ingredients in the freezer. This one has mushroom stems and celery!