What you will need:
Yogurt starter (plain or vanilla yogurt with active cultures)
We use our own milk that the cows make here on the farm. We like to make a lot at one time because we love it! So we fill 2 big kettles almost full of milk (but not too full or it may overflow once you add the yogurt starter).
Then you heat the milk on the stove top until it reaches 185 degrees F. Once it reaches that temperature, take it off the stove and immediately place the kettle in a cold water bath. We have a two compartment sink in the kitchen so we like to switch the water out once it gets warm. Cool the milk to 110 degrees F.
Take it out of the water bath and add 2 cups of yogurt starter, which is just plain yogurt with active cultures that be buy from the store or use from the last batch of yogurt that we made (other recipes don't use as much starter, but we think it might make the yogurt thicker. But that isn't always true, it's just what we like to do). Stir in the starter. Place the kettle in the oven with the lid on it, and turn the oven on to the "Warm" setting or 170 degrees F. When the oven is done preheating turn the heat off and let the yogurt sit for 6-8 hours. It has to be warm and dark for the cultures to turn the milk into yogurt so don't open the oven door too much and don't leave the oven light on. Reheat the oven every 2-3 hours (so 1-2 times), but do not leave the oven on for a long time or it can kill the cultures.
We find that it may take longer than 8 hours sometimes. Once when we made yogurt, we had it in the oven for about 20 hours (but that's because it should have been ready in the evening and it wasn't so we left it in overnight just because we didn't feel like cleaning everything up that night, but in the morning it had made yogurt!)
Once the yogurt is made, whisk it to make it smooth and stick it in the fridge to cool, and once cool, enjoy! You can add flavored gelatin, fruit, granola, jelly or jam, or make yogurt pancakes or muesli (I might get around to putting up a recipe for yogurt pancakes and muesli some time).