Might be someone who you think had a career success in your field (or a field you're interested in), or might be something else, but you admire this person. In any case you want to gain some useful knowledge, improving yourself.<p>What do you ask?
I would try to establish a friendship with them rather than trying to transactionally extract some useful knowledge.<p>Consider what you can offer them rather than what they can offer you.<p>“Would you let me buy you coffee or lunch some time?”<p>Find out what they are interested in outside of their career, or if they share any passions of yours.<p>Ask them what they’ve been reading, watching, or listening to lately. Then you could engage with that media yourself and have something interesting to talk to them about.<p>I suggest you read the book How to Win Friends and Influence People. Never Eat Alone is another book I’ve heard good things about on this subject.
Echoing what bckr said, try and see if there's something you can provide to the person you admire.<p>From the book: Superhuman Social_Skills: A Guide to Being Likeable, Winning Friends<p>'The value you're trying to convey is attributes about yourself that make you an interesting and pleasant person. You want to build intrigue without conveying arrogance, and demonstrate that you are socially adept, non-needy, and will be an asset to the person or group with whom you're interacting.'