You must be a very particular person to have seen or interacted with a celebrity in the wild more than once. Most importantly, you probably live in New York or LA. I love cities like Bethesda, Maryland, but you're probably not going to see Sandra Bullock walking around there. If you work in the entertainment industry, that also helps a lot with celeb spotting. Believe it or not, interviewing actors for media companies will put a lot of celebrities in front of you.
Everybody has a different approach when they meet a famous person. My strategy is to give them a very specific compliment if I'm familiar with their work (and then leave quickly) and to say nothing if I'm not familiar with their work. This has worked wonders on the zero celebrities that I've met in person. People who have actually met celebrities recently took to Twitter to share interactions they've had, and they are a real hoot.
