(excerpt from the book Stephen Johnson on Digital Photography unreleased revised electronic version)The photograph you may see will often only be a photograph you make if you are prepared to capture it.
Check existing settings that might be left from a previous situation that may be quite different than what you need now. Common problematic settings may be methods of focus, high ISO setting, Manual vs Auto exposure, Image Stabilization turned on and customized for the movement, or off if on a tripod.
Thinking through the ambient exposure and likely subject matter needs can anticipate a moment so that your camera is preset for what is likely.
Fast moving action means pre-setting a fast shutter speed, and possibly high ISO if limited light needs it.
As you walk down a street, consider what it is you are noticing, and prepare for possible unfolding events that needs quick response. Put on the most likely needed lens, but arrange the pack for other things you may need, the second most likely lens.
Although it may seem an unlikely pairing, being prepared also makes for a greater possibility of serendipity playing a wonderful role in recording the completely unexpected.
The dolphin photograph to the right could not exactly be seen, it was happening too quickly. The settings I set up were able to capture a magic I could intend, but not actually see and react to quickly enough to capture. I had to just set the camera and keep tripping the shutter, sometimes on continuous bursts and hope that some of the magic I was seeing could be held. It was, and more.