There is a lot of different methods to accomplish the same thing (great yogurt)
I have a Salton yogurt incubator ($20) that I fill with ultra pasteurized milk, 2T of Greek yogurt(after the 1st batch you can use your own yogurt for this step) and a bit of powdered milk for thickness and extra calcium.
Put all in the incubator and plug in!
Leave for 4 - 36 hours depending on the level of health benefits and tartness you desire!
I make a batch every 3rd day for our needs. Add jam or berries before serving if you want a flavored version.