Making stock always seemed to me to be one of those things that people did when they had an abundance of time, a greater abundance of skill, and a certain touch of fussiness to their cooking preferences. The first time I made it myself, I was shocked how easy making stock really was. It came out watery and a bit weaker than I expected, but I had made it all by myself, using things I would normally have thrown away. I've learned, since that time, how to make the stock rich and full of flavor.
Making stock is one of those things that yields great rewards, even with seemingly few resources going in. All you need are leftover vegetable scraps, an onion, maybe some herbs, and possibly some meaty bones of some sort if you want to make a chicken, beef, ham, or fish stock. I typically make chicken stock, as that's what I use the most in my cooking, and what I usually have on hand to use. I have made both beef stock and vegetable stock, and the same basic technique applies to all varieties.
I usually use the ends and bits and bobs of many recipes' worth of vegetables. I keep a large ziploc bag in the freezer to throw scraps into for stock so when I'm ready to make it I have all that I need. To these I add a few whole veggies, (stronger flavor than just the scraps,) and a leftover roast chicken, stripped of most of its meat. Alternately, I have used a whole chicken in the broth, which results in wonderful flavor, and you can strip the chicken afterwards for casseroles or soups. I usually only do this when I'm making chicken noodle soup, as all the stripped off chicken can go back into the pot once the broth has been strained. Once the stock is made, I cool the stock and refrigerate it. (You do want to let the stock cool on the counter a bit first, as putting it into the fridge while still warm can cause the stock to sour.) Once its cool, I remove any fat from the stock, as it's now cooled and hardened on the surface and can simply be lifted off. Then I freeze it in small portions so I can get as much stock as I need when I need it.
Assemble your vegetables. (This is the last time anything will look somewhat pretty, so enjoy it while you can.) You can use nearly anything, but an onion is a good base, skins, roots, and all. Carrots and celery back it up nicely, and from there, use whatever you have. Some people don't like using potatoes in their broth, as they can make it a bit cloudy, but I don't mind cloudiness and the flavor is nice. Tomatoes, also, are often questioned, as they can add a mild sweetness to the broth, but again, I don't mind, and in fact don't really notice that too much. You can add some fresh or dried herbs as well, but I honestly just plain forgot to, so they won't be in the pictures. :)
Throw everything in a large stockpot, including meaty bones if you're using them. I had a frozen roast chicken ready, so that's what I used this time.
Cover everything with water. Vegetables and bones tend to float, so this is within reason. The more water you add, the thinner the broth will be, unless you simmer for hours and hours. That's actually what I did, so I added lots of water.
Those bubbles, (and the stuff clinging to them) are something that you can choose to skim off for a clearer broth. I tend not to, as most of the stuff you're skimming will get stuck in the cooled fat. If you're using the broth the same day, skim. If you're making vegetable broth, don't worry! That stuff comes from meat, so it's not your problem. :)
This is what your stock will look like after a few hours of simmering. It will have reduced some, which is code for concentrated in flavor, and will be a golden color. (Unless its beef, and then it will be more brown.) Take a spoon here and taste a bit of the stock, and adjust for salt. Remember, its a really big pot of water, it'll probably need at least a tablespoon, but you can adjust to taste.
It's time to strain it! I don't have photos for this, as its hard to pour and take pictures at the same time. Basically, set a really large bowl in your sink, and place a colander or mesh strainer inside. Pour the stock into the strainer. Be careful of steam here! You may have to do this in batches, depending on the size of your bowl, and the size of your strainer. You can mash the vegetables in the strainer if you wish, which is great for getting extra flavor out, but also often means you have to strain again to get the bits you pushed through out.
Lovely finished stock! You can use this now, or let it cool overnight to get the extra fat out of it. Mine's a bit grainy looking because I didn't skim, as I'm planning on cooling it. Make sure you let the stock cool to room temp, or nearly to room temp, before putting it in the fridge. If its too warm going in, it can sour, and all the effort is wasted!
This is what the stock looks like the next day. A thin layer of fat covers the whole bowl. Obviously, if you have a deeper, narrower bowl, the layer of fat will be thicker and even easier to pull off, but it takes longer to cool down in a deeper bowl, so I went with my widest one. Take a spoon, or your fingers if you don't mind it, and peel off the fat. You may get a bit of stock coming off with the spoon, but mostly the fat will cling to it and the stock will drain. If you end up with a few small pieces left in the stock, not a problem! The moment the stock is heated the fat will reincorporate.
You're done! Freeze in various sized containers as you'll use it, or turn it into a lovely soup right away! (May I suggest chicken noodle soup?) Enjoy!