Taking a lot helps, but you also want to be directed. Directed practice has been discussed on HN numerous times at this point. For photography I would go to a location and take a lot of pics of the same thing using auto, aperture priority, shutter priority, and then full manual. Most of these would get thrown away, but I can see how each came out and use that to further improve.

This method of practicing and improving used to be expensive with film, but with digital the process is now free.

The other thing you learn is your camera shortcuts so that when you do run into a photographic moment you can quickly take a bunch of shots with different settings.