A colleague opens up to you and says that he's interviewing for a new job. He asks you to be his reference. Should you say yes? And if you do, how do you best convey the applicant's skills and expertise? Here's what you need to do.

1. Decide whether you want to give a reference.

If the person was a star performer and dedicated colleague, then the answer may be obvious. But if his track record was spotty or worse, be careful.

"You're putting your reputation on the line," says Jodi Glickman, founder of the communication consulting firm Great on the Job. "If you refer someone, and he doesn't perform, you look bad."

2. Be honest.

If you feel you really can't serve as a reference, say so, says Glickman. And if your appraisal of the candidate's abilities is mixed, Priscilla Claman, president of Career Strategies, advises having a "conversation [with the applicant] about what exactly you might say" to a reference checker.

3. Prepare.

When you do agree to give a reference, ask the candidate for assistance.

“If you don’t have enough information to speak off the cuff, or you worked with the person a long time ago, request an up-to-date CV and then have them refresh your memory on their top accomplishments at your organisation,” says Glickman.

4. Use specific examples.

Hiring managers are often interested in two key aspects of a candidate’s on-the-job performance:how the candidate relates to other colleagues, and his technical skills and expertise. In both cases, “be as specific as you can about the contributions” the candidate made to your organisation, says Claman.

5. Be positive.

“The level of enthusiasm you bring to the conversation and the superlatives you use to describe the candidate” should convey your opinion of the applicant’s abilities, says Glickman. “Never give a negative reference – it’s far too fraught.”

6. Follow up.

Many applicants are only vaguely aware of when and if their references are being checked, and so it’s a thoughtful gesture to “let the candidate know you spoke to the hiring manager”, says Claman. Jobseekers are often hungry for information about their fate in the selection process.

– Copyright Harvard Business Review 2015