Read this great article by David Fix on the BirdFellow blog HERE.
One bit of info I would tweak to fit the Atascosa Highlands CBC is which species of owls to imitate (or play tape/iPod of, if you don't whistle). Our Northern "Mountain" Pygmy-Owl toots 100 times per minute, not the 20-25 of the Pacific Northwest birds; often the notes are paired into double-toots, but not always, and still average out to 100/minute. Furthermore, screech-owl imitations are just as effective, if not more so in much of our area. Both Western and Whiskered Screech-Owls are common in the circle, and in addition to stirring up mixed flocks of Bridle Titmice, Ruby-crowned Kinglets, and the occasional Hepatic Tanger pair, you may also get a daytime response from a real owl. Keep in mind that Whiskered Screech-Owls tend to be in larger, denser stands of oaks, and Western Screech-Owls are usually in more scattered, open woodland with lots of open area between the trees.