I've been making my own "live" yogurt for more than 30 years. My mother-in-law was Syrian and she taught me the way she was taught. A gallon of milk in a heavy pot at medium heat brought to almost boiling - the point at which little bubbles begin to form around the edge, but no actual boiling has begun. Turn off heat and wait until the milk is at, and I quote, "the point at which you can put your pinkie finger in and count to ten, but by the time you get to ten you want your finger out now." Gently stir in at least one cup of starter culture. I use 1 - 2 cups of yogurt from a previous batch. If I don't have that for some reason, I buy a really good quality organic, live culture yogurt from the health food store. Cover the pot. Turn the oven on warm for no more than a couple of minutes to just warm the oven. TURN OVEN OFF. Place pot in oven for 8 to 10 hours, and you're done. I usually make yogurt in the evening and by morning we're all set. I have used raw and pasteurized milk, I have used whole and 2%. I would not use "ultra" pasteurized - which many dairies do now for longer shelf life - as the temps are high enough to kill the beneficial organisms. I would also not use skim or 1% as these produce a much thinner yogurt - thin way beyond what is desirable. Also, just as a side note, I make a product my mother-in-law called labneh (pronounced lub-nee) - and many natural food stores call "gourmet yogurt cheese" and charge a fortune for - by putting the yogurt in a muslin bag (you could use any cloth that will allow the liquid in the yogurt to drain out) and setting the bag in a colander over a bowl for a few hours. I use this in a lot of Mediterranean cooking, but I've also found that the chickens don't make nearly the mess with it because it's more a sour cream consistency. I save the drained liquid and give it to them also. They love it! A couple times a week I add a splash of organic ACV which they also love.