The right , says Harris, is someone you're comfortable working closely with who also has the respect of others in IT--both above and below them. Look for someone, for example, among your IT directors. A manager with some visibility outside of IT is also an asset, although he or she doesn't need specific business-side experience. Once you've identified that person, says Harris, "The first strategy is to tell them exactly what you're doing: 'I'm trying to groom you to take my job.'"

Then, place your ego in check. Part of letting go of control is realizing you can't--and don't have to--do everything. You'll know you're successful when you can trust that operations are running smoothly while you focus on strategy.

Plenty of up-and-coming IT leaders want the opportunity for on-the-job training that would position them to become second-in-command or a CIO. But Harris, who mentors future CIOs through the CIO Executive Council (a peer advisory service founded by CIO's publisher), sees few emerging leaders who have access to it. Surveys we've conducted in the last year suggest lack of time (39 percent) and opportunity (17 percent) are the greatest obstacles. Yet 53 percent of CIOs surveyed by the Council list developing leadership depth as a top priority. Harris thinks the disconnect stems from CIOs unable to let go a little. "I'm a victim of it myself. It's a control thing," he says. "Many CIOs just feel more comfortable on the technical side of things."

Meanwhile, build the case for an official number two. You may not be able to promise your alter ego more money or a promotion right away, and she'll have to do more work than is included in her job description. But you can promise her greater visibility, which will help to advance her career and your argument for having a designated deputy.

"Most companies will look at the bottom-line salary [of a deputy CIO role] and say no. But what happens if the CIO is hit by train?" asks Harris. "I always had a de facto number two in training."