I would definitely agree with all the above, even though I don't actually believe that a camera always helps. I simply guess that, righteously, some people don't want to be filmed. A couple of tips I used and still use from time to time:
1- At the very beginning I used to go to shopping malls with my friends and show them tricks, but I sort of did it trying to involve other people whom I didn't know (It's a lot easier to involve passersby if they see a group of people gathered around someone, for curiosity engages them and your job then is simply drawing them in, maybe with a polite and Brief introduction in between your patter lines);
2- I often do this thing when I want to perform for a bunch of strangers: I get a 20 euro bill, I write "magician's money" on it and then fold it. Then I approach a group, I politely ask a person if they could move just an inch and I produce the bill from very close to their feet. At this point, almost always tries to say something like "these are mine", and I tell them, I am pretty sure these are mine, as you can see (show them what you've written on the bill), and then proceed to show them a quick trick with the bill (floating, twenty to a fifty,...). I'd advise to do this only when pretty self-confident with your audience management skills.