I'm surprised no-one has mentioned
Motion-Id on flickr yet. A quick look through some of his street stuff will answer a lot of Gary's questions.
Street photography conforms to all the rules of photography - landscape, motorsport, portrait, whatever. Its always about nailing the composition, the light and the moment. You still need to pay attention to the rule of thirds. You still need to watch where the light's coming from. And you need to be in the right place at the right time.
Sure, you need the vision and the equipment - fast lens with decent bokeh will always help - but I guess most of all you just need to get out there and do it.
Now if someone could pass me the cojones, then I'd demonstrate. I find street photography really difficult to do. It makes me feel self conscious and I hate the fact that I'm drawing attention to myself. I applaud anyone who can make a decent job of it. Its not easy.