Shutter sound off, flash off, messing around with my phone's camera while I look like i am playing games on it.
The idea itself is not even mine, I nicked it off a friend and past collaborator (I made the soundtrack for an exhibition of his based on pictures of people he took on the tube) who used a real camera to take the shots, and some great shots they are indeed. It was more difficult for him because he had to look like a photography student messing around with his big camera on the train, which is all the more surprising given the results often seem staged.
His website:
http://www.markfwilkinson.com/index_f.htm