Fig. to talk with someone to find out information about something.
According to ehow:
When you really want to get someone's ideas or feelings about a subject, you need to learn to pick their brain. Tapping into someone else's experience and inspiration doesn't require literal brain surgery, but it does take a deft touch to elicit ideas carefully. Here's how to pick someone's brain.
Step 1 Approach your subject carefully. You want to make the person feel comfortable sharing ideas and insights with you. Don't push the person to reveal more than he wants to. Give the person an advance look at your questions or discussion topics if possible, to allow him to organize his thoughts.
Step 2 Frame good questions. Nobody has all day for you to do a Vulcan mind meld and download everything they know about every subject. Choose several key areas to explore, and take notes or record your conversation so you won't have to go back and ask everything again.
Step 3 Accept your subject's insights uncritically. You've come to pick this person's brain because you believe they have valuable information, so don't be critical of or argumentative about what she has to say.
Step 4 Pay attention to body language. Learning nonverbal cues is crucial to picking someone's brain. People say a lot without speaking, and you can learn from what's unsaid, too.
Step 5 Agree to return the favor. When you've benefited from picking someone's brain, it's a good deed to volunteer yourself for a similar exercise at another time, when your own insights and experience might be of equal value to someone else.Just in case you were wondering!