I'd say I try to make small talk with him. I think that's one of the hardest things to do as far as Michael is concerned.
There's always throngs of chaotic people and cameras and security. But just to be face-to-face with him alone, in a quiet setting, MAN lol.
I'd tell him I'm an enormous fan, and then try to ask him how he's doing, how's the family etc.
Someone said it earlier, Michael's said he's always wanted to know how ordinary folks interact. He's said that everytime he meets people they're going crazy or they want something from him, or trying to give him their business card etc.
Obviously it's Michael effin' JACKSON lol, so it's easier said then done lol. But I'd try to talk to him as MJ the man not MJ the entertainer, so he'd feel comfortable and unthreatened. ^_^