I've done my share of reference calls in my career and to be honest, the majority were basically crap. This isn't to say that I am the best individual when it comes to making reference calls but in hindsight I always wondered whether I benefited at all. Further, I always ended up questioning more why the person whom I spoke to was actually given as a reference. My personal opinion as to whom you want to call when referencing me is people who probably hate my guts. Even better, call those who think I'm a complete idiot. They'll probably go on for hours giving you wonderful information as opposed to someone who is just cheerleading for me.
Therefore, this post is not about what to ask when doing a reference call. It's about what to say when you are the person being asked to give a reference. Seriously, on a reference call, you want the person whom you call to do all the talking. If you have to ask too many questions, you already know they suck. Honestly, most people aren't often called and asked to give a reference. I've on the other hand probably done 100 reference calls at this point in my career for either individuals seeking a job, VC's raising funds, entrepreneurs raising capital, candidates applying for grants, students applying to schools and the cops have called me a couple times too (but we'll keep those details to ourselves!)
So what is it that you should talk about when called and asked to be a reference for someone? First and foremost, talk about who they are. Do you really want to try and paint a pretty picture of someone, leading them to land in a shit job that doesn't fit their personality or career path? I don't!
Further, discuss what they are really good at. No one really should be trying to focus on their weaknesses. Most people are being chosen for their strengths. Focus on this when talking about them. Impress me and tell me everything you think they are really good at. Trust me, people want to hear the good stuff. If someone is an excellent cook but is trying to raise a fund....who cares, go ahead and talk about it. It shows they have a life outside of the office. It also shows that you know this person.
Don't shy away from things that aren't necessarily considered positive. If I think someone has hated being a sales guy because he secretly wants to be a developer, I say so...even if they are applying for a sales job. You never actually know what was discussed between the other two parties. You also never know what the interviewer is really trying to get at. Don't try to figure it out. Go in depth about what you know. If you don't know, please say so and don't try to figure out an answer. It often ends up painting a false picture and you are doing everyone a disservice.
Feel free to focus on personal stuff. I've told interviewers that someone is a great person but she is going through a divorce now and may be distracted. Really, why not give this information? In this case, I know that the candidate was relieved to be able to vent about her personal stress and the employer ended up accommodating her. Her boss had also gone through a divorce. She is still in that job and loves it. I've also discussed someone who was an alcoholic and went to rehab. I was fascinated by their development and how well they overcame a really shitty part of their lives. I would of hired this individual in a snap. The interviewer did and this candidate is a huge benefit to that organization.
Don't obviously when being interviewed bitch about someone and say things you wouldn't tell them directly. If you were mistakenly given as a reference and have an axe to grind, don't be a wimp and do so directly with someone. I make a point of calling back everyone I give a reference for and discussing exactly what I said about them. I want them to know what details were given and make sure they don't walk into a situation they aren't prepared for. Not one call has ever led me to regret being candid and/or having gone in depth into this person's traits. Folks were often surprised at how detailed or open I was with my feedback but I always explained my motives and I don't feel that I've ever led anyone to be in a worse off situation after someone interviewed me.
Finally, if you can't be a reference for someone, say so. I've been called a couple times and couldn't even remember who the person was. I was completely up front with this information. I always made a point of saying how well I know someone and how much interaction I had with them. It's not a vanity thing to be interviewed and if you don't have anything interesting to say about someone, skip being a reference for them. You're otherwise just wasting your time and other people's time.