Take 1 liter of milk (I take home), heated it to body temperature, i.e., dipping a finger there, if the heat is pleasant, it is enough to warm.

Warm milk I poured into a thermos with a glass bulb, if not, you can in the jar. Into the milk add 2 tablespoons of starter culture (in my case it's the sour milk that is left over from previous times). If yogurt or Kislyak no, take ordinary store-bought yogurt is not long shelf life, and pour 1 Cup of the milk. Mix well. I have to add yeast with a slide... like the picture.

Close the thermos and leave overnight, if you do in the morning, until the evening. If you make yogurt in the Bank, have the Bank cover with a clean towel, and wrap in something warm, until I had a thermos I had wrapped in a shawl and put this structure in a package like this heat very well preserved.