I love yogurt, but it can be expensive. Especially if you buy it in those cute little individiual serving cups with the foil lids. Store bought yogurt often has preservitives, stabilizers, thickening agents and loads of sugar. And talk about excess packaging. Thankfully yogurt is very easy to make at home, and no, you don't need any fancy equipment. Just a quart sized jar, a few tablespoons of prepared yogurt (either store bought or from a previous homemade batch) and a place to keep it warm.
If you're using store bought milk, you'll want to pasturize it first, to make sure there are no organisms present to compete with the yogurt cultures. Put 1 qt of milk into a small sauce pan and heat to 180*, stirring frequently. If you don't have a thermometer, this is not rocket science. Just heat it to just before it boils, and then turn off the heat. Let it cool down to about 110*. If you're using raw milk, just heat gently to 110* so as not to distroy the benificial enzymes in the milk. Once the milk is at about 110*, stir in about 1/4 cup of prepared yogurt. For your first time, it's fine to use store bought yogurt. Just make sure you get one with live active cultures. Dannon is a good brand that's easy to find. I like to use Brown Cow, found in Whole Foods or the healh food section of a regular grocery store. It's easiest if you stir a little milk into the yogurt first, and then stir the thinned yogurt into the rest of the milk. Then pour it into your quart sized jar, and rubberband a towel or coffee filter over the mouth of the jar.
Now all that's left is to find a way to keep it at about 110* for the next 8-18 hours. There are several methods for doing this. I have a gas oven with a pilot light, so I just pop it in there and leave it. Similarly, if you have an electric oven you can put it in with the oven light on. Beware with using your oven, if you need your oven to cook dinner, remove your yogurt before preheating your oven or you'll kill your culture. In my last apartment my oven didn't have a pilot light or an oven light, so I had to get a little more creative. I bought a heating pad (like for a bad back) for about $9 at a drug store. I would put my yogurt on the heating pad on low, and cover the whole thing with a dishtowel for insulation, and this worked fine. Some other methods are to use your crockpot on the warm setting with water surrounding your jar, or using a small insulated cooler with warm water, of find a yogurt maker at a thrift store and let it do the incubating. I haven't tried any of these, but have heard good results from people who have.
The yogurt needs to stay warm from 8-18 hours. The longer you incubate it, the thicker and more tart it will be. I usually aim for about 10 hours, but the process is flexable. When it's done, just pop a lid on your jar and toss it into the fridge. I like to flavor my yogurt as I'm eating it, so that I always have plain yogurt in the fridge for starting my next batch. I like to stir in maple syrup (as in the first photo) or honey. You can also use jam for fruit yogurt, and it wouldn't be bad with a little chocolate syrup if you're feeling particularly naughty.