I have been photographing people on the street for years. My experience is that generally they are unaware that I am doing so and extremely rarely do I get a negative response. You need to know your equipment inside out and be able to use it instinctively, rapidly and smoothly - I use an RF, generally with a 35mm lens, but sometimes a 28 or 21, focused to either 2 or 3m, and work quickly Body language is important, you have to feel positive, respect your subjects and smile if you get eye contact. Practice helps! Have a look at the photos on my web site.
http://johnbeeching.com/

Yours,

John