Black and white was the original street photography mode. The shots have a timelessness that can't be captured in the same way as when shooting in colour. They give off a certain type of feel. A strong nostalgic and simple feel.
I don't shoot in black and white as often as I do in colour. However when I do, I try and think in black and white. When looking for a good composition or subject it helps to think this way. It sounds a bit weird but with practice and if you go out with this at front of mind it will become easy. There are digital options to set your camera to a monochrome preset, but I quite like the challenge of seeing in colour and converting this to black and white. I think its a good skill to have. You will begin to see and realise what works in black and white and this will come forward within the shots you capture.
Nico Goodden and Erik Kim have both written great blogs on shooting street photography in black and white. Giving yourself the constraint of shooting in black and white can actually let you see the shots in a different way. The images become less cluttered, with this in mind it makes sense to concentrate the image on a single or less objects. This will create a powerful capture.
Below are some of the photos that I have made, half shot in London and the other half shot in Frinton.