How to Make Sour Cream From Plain Yogurt

Easy!  You take plain yogurt(no additives), drain off the liquid(whey), add some lemon, and refrigerate for two hours. See here for detailed recipe.

This tutorial mentions the use of a fine mesh kitchen sieve to drain the yogurt, but cheese cloth or a strong paper towel over a colander works well too. I use the colander/paper towel combination over a large bowl to drain the yogurt. Instead of discarding the drainage(whey), save it for baking and cooking. I use whey in homemade bread.

For something extra, save a portion of the drained yogurt; skip the lemon, drain overnight, and you'll have creamy cheese!

Image for wikipedia.