When an associate wins at Dallas’ Cowles & Thompson P.C., Jim Cowles scrawls “GTL” in magic marker and hangs the sign on the lawyer’s door. One newbie thought that it stood for “Gone to Lunch.” He made his own sign and hung it up every day until he figured out the truth: “GTL” stands for “Great Trial Lawyer.”

Associates treasure their GTL signs, and work hard to earn them. “It’s a silly little thing, but it just works,” says Mr. Cowles. He understands the magic of incentives.