The main aim of street photography is to capture those moments which take place for a fleeting second, it can be an alignment of the street furniture which makes an interesting pattern, an interaction between two people on the street, or something as simple as the unexpected lack of an item on the street.
For instance; I have a friend who currently only takes photos of faces which appear from random patterns in the street, this can be windows, puddles or lights. He may take only a handful of photos on a walk but those he shoots look great.
Street photography has two key styles; in your face photos of people during their daily life or a more reserved stand back to keep an eye on the world around you.
I'm of the second school and like to observe and watch the oddity that is human life, I love to see how street scenes are different in each country I visit, but still have those same basic qualities of people going about their business.
Street Photography shouldn't be mistaken with street portraiture; that is pictures of people on the street. Street photography tries to capture living and the some of the bigger questions in life. The beauty of street photography is you don't need a fancy camera, just a keen eye and a sense of humour.
So get out onto your local street, have the confidence to take the shots that speak to you, and once you are comfortable being out and about with your camera, chat to some of the interesting people you meet along the way. If you're lucky, they'll let you snap them too.