I make it a lot. Now that there is just DH and me at home, we can't use a gallon of milk before it goes bad. Instead of buying a half gallon of milk, a quart of yogurt, a brick of cream cheese, a quart of buttermilk, and a pint of sour cream, I make half a gallon of yogurt.
Once the yogurt is made but before it is put in the refrigerator, I take out 2 cups or so, and let it stand in a warm place for a bit longer. I want this portion to get tangy so I can use it to replace the sour cream. Once I like how tangy it is, I refrigerate it also.
Once the rest of the yogurt is cold, I place it in a strainer, cover it, and let if drain for a couple of hours. If I want to use some as Greek yogurt, I take that portion out of the strainer after just a couple of hours. I don't want my yogurt too dry.
I leave the rest of the yogurt to drain until it is fairly dry, usually overnight. I take the dry yogurt out and put it in a container to use as I would cream cheese. I think it's very much like the cheese you find called Farmers' Cheese. It's spreadable, with just a bit of tang. It takes a time or two of making it to determine just how dry you want yours to be. If you want it to be easily spreadable, don't let it drain as long. Prefer something drier that you can shape into a block and cut, let it drain longer.
The whey that drains from the yogurt is a great substitute for buttermilk. It has lots of protein and is acidic, so it's perfect for recipes where the buttermilk would be providing the acid necessary to make something rise, say biscuits.
So, to actually make the yogurt, I start with finding a yogurt culture that I like. I found one on Amazon
Yogurt Starter that isn't too sour or tangy, but it can get that way if you leave it out a bit longer. When I use this starter, I freeze the first batch of yogurt in 1/4 cup to 1/2 cup portions. I use one portion immediately to make a new batch of yogurt. You can save some of each batch to make the next batch, but I find that with the dried starters each successive batch is less tasty and by the 3rd generation, it's not good. I also use cultures from yogurts at the grocery store. I find a yogurt I like and I buy a plain cup of it. You do have to check to make sure the ingredients list includes 'live active cultures' as one of the ingredients.
I start with 1/2 gallon of milk and I add 1/2 cup of powdered non-fat milk to it. Stir until the powder has dissolved. The powdered milk adds protein and makes the yogurt thicker. Heat the milk slowly, stirring frequently, until it reaches 180*. You can stop at a lower temperature, but the yogurt won't thicken as much.
Once the milk hits 180*, take it off the heat and pour it into something to cool. It needs to cool down to 110* before you add the yogurt starter. If you are using remade yogurt as your culture starter, take it out of the fridge and let it come to room temperature so the cultures will be active as they hit the warm milk. Once the milk has cooled, add the culture or yogurt to it and pour it into whatever you are going to use to let it ripen. You want to keep the yogurt at 100*-110* for the next 8-12 hours.
Here's where you can get creative. People have come up with a number of ways to keep the yogurt as close to the ideal temps as possible. I do one of 3 things. I set the bowl in the oven with the oven turned on to the proof setting (100*) and leave it for about 8 hours or overnight. My oven has a timer,so I can have it turn off after 8 hours and it will hold the heat really well for another 4 hours or so. This usually makes the tangiest yogurt. I can put the yogurt in the middle crock of my 3 mini crockpot set. I fill the other 2 crooks up with warm water and turn them on low or warm. A towel over the whole set up keeps everything toasty until I turn it off. My 3rd option is to take my big crock pot and fill it half full of water and set it to warm. I turn the lid over and set my bowl on top of it, with a towel over the whole setup. My big crock cooks pretty hot, so the warm setting is just right to keep the yogurt going.
After an hour or two, I do usually check the temp of the yogurt with a thermometer. It should be about 100*. 110* is ok, but you don't want it much over that. The cultures usually die at 120*, so cooler is better than warmer. If I am going to bed before the yogurt is done and I'm not using my oven setup with the auto turn off, I usually turn off the appliance and throw another towel over setup. As long as I don't sleep in until noon, this isn't a problem.
So far, I've had really good luck with my yogurt making. For a while I was also making Kefir regularly, but when DD left for China, I forgot to feed my grains and they died.
HTH,
Marcy
Jinx!