Have them program something in the interview. Watch them use their chosen text editor as they work through your problem. Have them run their program and watch them iterate through a few code/test/debug cycles. Once it's working, ask them for a minor but logical improvement, and watch their reaction. Dread at having to go back to the code, or gusto in making it better? How fast can they go back and edit their own code?

For whatever job you're hiring for, have them do the job as part of the interview process.