The best urban photographers always have a camera with them. The strap is usually around their neck or wrapped around their right wrist -- in either case, it the camera always at the ready. The point is, it isn't in a bag or tucked into a pocket. "To hit the decisive moment," says Jake Shivery, proprietor of Blue Moon Camera and Machine in Portland, Ore., "you have to be able to lift the camera to your eye."
To that end, make sure the lens cap is off before you head out with the camera. Also, it can be helpful to use a wide-angle lens if you've got an SLR or DSLR with interchangeable lenses. That doesn't mean you need to buy a lot of gear -- in fact, just the opposite. Get really good with your camera and one or two lenses and you'll get the street shots that you're looking for.
If you've always got your camera at hand, the next tip will come naturally.