I've always wanted to bake sourdough breads, but for some reason, I found the idea of making (and caring for) a starter somewhat scary. A few weeks ago, I finally got up the nerve to try it, and guess what? It's not difficult at all! Here's a basic recipe:
1 package dry yeast
2 cups warm water
2 cups all-purpose flour
In a large glass bowl, mix together the yeast and water until the yeast is thorougly dissolved. Add the flour and whisk until there are no lumps. Cover with a piece of cheesecloth or a towel, and store in a warm, draft-free place. Allow it to ferment for about 48 hours, stirring a couple of times per day.
You'll notice bubbles forming, and a clear liquid that separates to the top -- simply stir that back in. If the liquid on top is pink, throw out the whole thing and start over. After two days you can store your starter in the refrigerator.
Whenever you use some of your starter (or sponge), replenish it with equal amounts of flour and warm water. Your starter should be replenished at least once per week. If you do not make breads that often, take some out to share with family and friends.