Ever walk away from interviewing a potential employee, wondering if you just met the perfect match for your company or someone who’s simply great at interviews? I do. Interviews tell very little about a possible hire’s character, work habits, and personality. In a half-hour, you may be impressed by the strengths they flaunt, but learn little about how they might contribute to—and mesh with—your company. That’s why it’s vitally important to take advantage of the internship process.

It’s easy to think of internships as cheap or free labor drawn from a revolving pool of students you’ll never see after the semester ends. But internships are win-win situations for business owners—and a resource you should profit from. These students are looking for real-world experience and you’ve got months to evaluate intangibles that would never surface in an interview.

The key to effectively assessing those intangibles is not letting the interns know they’re on an extended interview. Observe where each intern’s talents and passions lie, carefully not pigeonholing any individual. In the months an intern is with your company, you’ll glimpse such qualities as attention to detail, enthusiasm, and follow-up. These are the types of core personality traits that are hardest to detect in a simple job interview.

You may very well wind up with lazy interns who are best-suited to collate papers and remove staples. That’s fine. You now know you wouldn’t want to hire them and you can be happy you didn’t. Then there are the eager, motivated, professional interns who want to learn and earn a spot with your company when they graduate. These are the new employees you’re confident in hiring—and they’ve already got experience with your company.

This article was written by Jim Belosic and published in Bloomberg Businessweek magazine.