Great article from HR Test on how to discover what candidates have done before:
To answer this issue, you have several options, including:
1a) Asking them to describe what they've done--the so-called "behavioral interviewing" technique. Research shows that these types of questions generally contribute a significant amount of validity to the process. But they're not perfect by any means, particularly with people with bad memories about themselves. And keep in mind at that point you're taking their word for it.
1b) Asking them for examples of what they've done. Best used as a follow-up to a claim, but tricky in any situation where there's even a remote possibility that someone else did it or did most of it (so practically everything outside of the person being videotaped).
1c) Asking others (e.g., co-workers, supervisors) what the candidate's done. Probably the most promising but most difficult data to accurately capture. Hypothetically if the person has any job history at all they've left a trail of accomplishments and failures, as well as a reliable pattern of responding to situations. This is the promise of reference checks that so often is either squandered ("I don't have time") or stymied ("They just gave me name, title, and employment dates"). Don't use these excuses, investigate.
Full posting here.