I make at least one batch of greek yogurt a week in the crockpot, It is soooo easy and is a big savings and so healthy. Once you get the hang of it, you can make it in your sleep literally. You heat the milk up in the crockpot for about 2.5 hrs on high. Then let the milk cool covered in the crockpot for 2.5-3 hrs unplugged. After it has cooled but still warm add one container, small, of greek or reg. plain yougurt and wisk. Cover place some dish towels on the crock pot to keep warm and in about 10-12 hours you have a huge batch of greek yogurt, unplugged of course. For $3 dollars you have like 15 servings, and you can use that batch, a cup of it, as your starter next time.
Must have live cultures in the yougurt, must be plain.
If you google it, you will get exact temps and time, it is almost impossible to screw up.