"Hiya! Wanna see some magic?"

[Albert]

I've learned to approach people, if I want to show magic, by saying something like "Hi, I'm a performer. Would you like to see something amazing?"
This gives the spectators something to question most often, like "What kind of performer? What's this amazing something? Now I'm curious and I want to see it."

I believe this is a more direct approach and it seems to work pretty well.