I just used a simple recipe that I found here. . . http://www.io.com/~sjohn/sour.htm
. It was straight forward and within no time I had a fully functioning starter. I didn't even use Caputo flour for my starter, I just use unbleached organic all purpose. Also, there are other ways to cultivate wild yeast using fruits and juices. Both of which are pretty well documented on this forum. Just do a search for "wild yeast" and "fruit". A word of advice: use your starter regularly at first (or at the very least feed it regularly at first) so you can get a good handle on how it works and how it is evolving. I noticed many differences in flavor and activity that developed over a short amount of time. This is probably because it hadn't fully developed yet. You will know you are ready to rock when it smells good and is active. (it will smell like wine or beer and bubbles to a froth.)
Additionally, there are starters that Marco, a forum member and long time contributor, has made available for purchase. Just go check out this website. . . http://www.sourdo.com/culture.htm
. There is a wealth of information there as well.
I wish you the best of luck.