Interviewing and assessing sales talent is super hard. I've literally interviewed thousands of sales people and sales executives and I still struggle with separating the great ones from the rest of the pack. One technique that I find very helpful is role playing. For me its the absolute best way to get a preview of what the candidate will actually be like once they are in the job.
I've had the good fortune to interview over 10,000 technology sales executives and as a result I've gotten really good at identifying patterns in top performers. One pattern I'd like to discuss / share is that endurance athletes tend to be great sales people.