I use whole or 2% milk. It makes a thicker yogurt.
I do about 3 quarts at a time. I slowly heat the milk in a pot, checking the temperature and stirring occasionally, till it reaches about 180 degrees. Then I remove it from the burner and let it cool to below 110. If it's too hot, it will kill the yogurt starter.
I used Dannon plain yogurt as starter when I don't have my homemade yogurt on hand. I add about half a cup or so into the cooled milk and whisk well. Then I pour the milk into 3 clean quart jars.
I put the jars somewhere warm..right now that is on my counter near the heating vent in my kitchen. I cover them with a warm towel and let sit overnight. They'll be set up by morning. You do not want them to get too warm, or you will kill the yogurt starter. In the winter, I keep the jars covered inside my oven, with the oven light on overnight.
You can let them sit a bit longer if you want it thicker, or more tart.
Cover and store in the fridge.
I use it in homemade smoothies, or over frozen blueberries, and drizzled with honey.
Good stuff! Easy. Much cheaper than store bought.