I make sourdough now and again. I make my starter with flour and water (just your normal homebrand white flour though jamie oliver says you "must" get organic stoneground stuff, it's worked with homebrand for me!)

I also "cheat" by adding some yeast to the bread when I'm mixing up the starter with the rest of ingredients. That way I get the sourdough flavour with an helping hand for the rise!

All the best - mine's always worked out so it's not tooo hard! Yumo!