Pretty much is what Christopher just said. Go up to them have a friendly chat. Say hi and you can just simply say so how's your day going. Ask about what they've bought or compliment them. One time I was at the mall with friends and I had a deck of cards that's exactly what I did. Went up to a group of people said hi asked about what they bought naturally they showed me some of their cloths and I'm just like those are awesome I'm betting they look great on you. After they asked what I bought so I brought out my cards and they asked if I played poker, told them I was a Magician and they asked me if I could show them something. If you build a rapport from the start people will be more willing to let you show them something. I used to just approach people and say hey wanna see magic or wanna see something cool and most of the time they denied me. Another thing I could tell you is look at their body language if they seem busy or Annoyed those people will most likely turn you down. Like always be confident, with yourself and your approach and remember that not everyone will want to see magic. If they say no then move on to the next group no harm done.
