Heat 4 to 5 cups milk (for most yogurt makers) in a large saucepan to 185 degrees F. Allow to cool to 110 degrees F.
Combine ½ cup plain yogurt OR 1 ½ teaspoons to 3 tablespoons powdered starter with a bit of the warm milk, and whisk the mixture into the rest of the milk. (Note: to see how much powdered starter you need, follow the directions of that particular starter.)
Transfer to the small cups of the yogurt maker and let culture for 5 to 7 hours, or until set. Refrigerate for 2 hours before eating.
Alana Chernila writes, cooks, sells fresh vegetables, teaches cooking and cheesemaking, and blogs at EatingFromTheGroundUp.com. She is the author of two books, The Homemade Pantry:101 Foods You Can Stop Buying and Start Making, and The Homemade Kitchen: Recipes for Cooking with Pleasure. She lives with her husband and daughters in western Massachusetts.