make a batter with milk and let it sit for hours and then use some of that and put the rest back

That sounds closest to what we used in the bakery, way back when. I've never done it at home, though - I did all the baking I'll ever need to do in my life when I did it for a living. Good luck.

All I know is the more of the clear liquid you include, the more sour the bread will be.

(Why oh why am I not there with you trying to figure this out? Stupid broke specklets and stupid expensive rental cars!)

well, it all basically boils down to the quality/quantity of the wild yeast that's in the air. some old wives' tales that used to circulate around baking in the region i grew up in (midwest) have it that old buildings where much baking has been done are more suited to making a good starter.

similar tales and superstitions / etc. revolve around the making of lambic in Belgium (sour fruit beers) for the same reasons. you need an ample quantity of the 'right kinds' of wild yeasts floating around in order for the starter to taste good and leaven properly.

you can also 'seed' starter from someone else's, if you know of someone who has a great sourdough recipe.

my mom used to bake sourdough. her starter was kickass, but then, we were in a 130-year-old farmhouse where it was pretty much accepted that there'd been a lot of home baking done there over the years. yeasts can stay dormant for decades, so continuity isn't as important as age.

or you could skip all that mess and just make sure you've got good active commercial yeast. far more predictable results, ya know.

rec.food.sourdough is the canonical resource. rec.food.sourdough FAQ is the distilled wisdom of that group.

Thanks everyone, and wow, paulsc--what an excellent resource. Many thanks for those links.