FORTUNE — Your deputy is the one position at your company that you shouldn’t head hunt. It’s best to bring in someone you’ve worked with successfully in the past, so you can hit the ground running from day one.
Don’t limit your list to past colleagues. They can be clients, suppliers, family members, and childhood buddies. When I founded the Young Entrepreneurs Organization (now EO), my right hand was a former student from an adjunct teaching gig who had impressed me. Bill Gates and Steve Ballmer were poker-playing buddies in college, long before Ballmer became CEO at Microsoft (MSFT).
What should you look for in this person? Remember that in today’s business environment, you’ve got to stay market-focused to win. For your No. 2, you need someone who’s good at putting out fires and executing your best ideas. Otherwise, you’ll be living the nightmare many entrepreneurs face: Doing everything yourself, because there’s no one around you who can. You also need someone who can be a shock absorber between your grandiose ideas and your team — or, like many entrepreneurs, you’ll drive your people crazy.
Once you have an idea of who’s available among your top candidates, look for short-term opportunities to collaborate. Maybe there’s a board of advisers position open at your company — Eric Schmidt served on Google’s (GOOG) board of directors before he became CEO — or a paid consulting gig. This will give you a feel for how well you will work together in your current company. You need to know you can fight with this person without resorting to fisticuffs.
When you feel like you’ve found the right person, even if you know each other well, do a detailed, formal interview, where you use an objective scoring system to evaluate candidates. Ask what they liked about their past positions and bosses. I once got very close to hiring a highly qualified right hand I had known for many years until I did an interview like this and realized that the common thread among the past managers she’d loved was their availability to mentor her. I wasn’t going to be available to do that much, because I travel a lot, so I decided it wasn’t a good fit.
It can take time to find the right deputy, but it’s worth it. Entrepreneurial companies tend to do better when they are team-led, as Harvard Professor Noam Wasserman discusses in The Founder’s Dilemmas. Not every entrepreneur is lucky enough to find the perfect co-founders, but if you later pick an amazing No. 2, you’ll be able to reap many of the same rewards.