Interview the most boring person you can find (though, don't admit he/she is boring) and try to get him/her to open up on the interesting parts of his/her life. Everyone has something fascinating, bring it out!
What are your perceptions of him/her now? How would your bland-appearing character benefit from this "diving expedition" approach?
*You can also do an interview with someone you think you know well and try to find out things you didn't know and/or expect.*