Answer:
Congratulations — you’re finally in the same room as your favorite celebrity! Take a deep breath; you’ve gotta do this right. This is someone you LOVE, and you want him or her to like you back, right? So make sure you’re in a situation where it makes sense to introduce yourself. Generally, If you don’t take up much of their time, celebs are happy to meet someone who appreciates their work. So if you’re in a doctor’s waiting room and you see Kristin Chenoweth, don’t ask for her autograph! On the street, at a coffee shop, at the theatre, or a similar innocuous public locale, it’s generally acceptable to say hello, and a sure bet is spotting a star at an event like BroadwayCon, which comes with the expectation of fan presence (celebrities show up knowing — and even hoping! — that they will be approached). Listen to your gut and you’ll be golden!
Establish eye contact organically, if you can do so without staring; in the absence of that opportunity, simply approach and say “excuse me” or “hi” and tell the star your name. Friendly eye contact with a smile, in any circumstance (even in any language!), says “I appreciate you; I respect you.” It’s the right way to begin any interaction that you want to go well.
If it’s not a good time, you’ll get a polite but cooler response; be attuned to signals like lack of eye contact, shifting from foot to foot, or keeping his or her body turned away from you.
Don’t dilute the experience with statements like “I never do this” or “I don’t want to waste your time.” Not only are these comments unnecessary time-sucks, but neither of them really holds water: you can’t claim to “never” do something that you're in the process of doing, and statements about wasting time are what actually take up time!
Humans (including celebrities!) are programmed to relate to those with whom we share something: a common interest, a mutual friend, a shared history or experience. An exclamation like “Omigod I love you,” while complementary, establishes a differential in power and comes across as generic and unmemorable. Instead, try “I saw you in The Color Purple in 2005 and it has been my favorite musical ever since.” If you’re tongue-tied, “thank you for what you do” is always a fantastic go-to.