This is the starter that goes with Classic Sourdough Bread that I posted earlier. Sorry for the oversight.
Note: This does not include the 2-3 days feeding time or the wait time for it to become full strength.
Dissolve yeast in water in a large plastic container (gallon size works well). Add sugar. When yeast bubbles (about 10 minutes), stir in flour until you have a smooth paste.
Cover loosely to allow gases to escape and place in a warm spot in your kitchen 2 to 3 days. The mixture should bubble and give off a sour odor. Stir starter once a day, making sure to stir in any crust that's formed. After this point, you can store starter in the refrigerator or leave it out in a cool, dark area of your kitchen.
Feed starter by stirring in 1 cup all-purpose flour and 1/2 cup water every day if you leave it out, or every few days if it's refrigerated; otherwise, it will become too acidic and eventually die.
Once starter has grown a few weeks and has reached full strength, you can decrease feedings to once a week.
If you don't use your starter regularly, it's going to get unruly and burst the bounds of it's container. Give some away to friends along with feeding and baking instructions.