Here is what you will need:
5 quarts of milk
1 and 1/2 cup plain yogurt
6 quart pan
dehydrator or whatever heat source you choose
canning jars/plastic containers
whatever fruit/sweetener you want to add
Here we go: I use one gallon of whole milk, plus one quart of half and half or cream. You can use any combination of milk, you will just need about 5 quarts for this recipe. We eat a lot of yogurt in my house, so if you do not want to make this much at one time, just use less milk. Use at least a six quart pan, add milk and heat to just about boiling (170-180 degrees). Stir frequently so it does not burn. (use medium heat). Next you need to cool the milk to about 115 degrees. You could do this by, letting it sit outside during the cold months, putting in the fridge or freezer, or setting it in an ice bath until it reaches the needed temperature. Then out of the milk take about 1 and 1/2 cups, put in separate bowl and add 1 and 1/2 cups of plain yogurt. Any yogurt will work, I usually use Stonyfield farms. Whatever starter you use, it should only contain milk or milk solids and bacterial culture: Lactobucillus, bulgaricus, L. acidophilus, and S. thermophilus. Avoid ones that contain bifidus. After making your first batch you could keep 1 and 1/2 cups of this back to make you next batch. Some say that you can only do this a couple of times before you need to use plain yogurt again. But if you make it enough, I have found that this is not a problem. After mixing the small amount of milk and starter, put back into large batch and stir to mix well. Pour milk into jars or plastic containers. I use glass canning jars (any size). Place lid on jars or containers, do not tighten. Place into dehydrator, I use the Excalibur 3926 TW 9 tray. But you can use any dehydrator. I use this one because of the space it provides, and because I use it for lots of other things. There is also other ways to get the same results if you do not have or want to purchase a dehydrator. Just do a search on google. Other ways that I have read about, but not tried are; your oven, slow cooker, cooler filled with hot water! When using a dehydrator you set it to 110 degrees and set timer for 12-24 hours. Depending on your preference of tartness. The longer it ferments, the more tart and thicker it will be. You can set it for as little as 4 hours but it will not turn out as thick. If you are lactose intolerant, fermenting the milk for 24 hours will virtually eliminate all of the milk sugar (lactose). When the dehydrator is finished screw band on. Let cool, and then place in fridge for 8-10 hours. It will thicken as it cools, You can eat it at this point or strain the yogurt by placing 3 layers of cheese cloth in a colander removing the whey it what makes it Greek). Set the colander in a bowl that is slightly larger so that the whey (liquid) will drain. Dump the whey from the bowl every few hours, so that the yogurt does not sit in it. I usually let it drain for 10-12 hours. There you go, it is done! You can add whatever tickles your fancy. I usually add honey, vanilla and/or homemade granola.