Filters and Long Exposures
Filter use combined with long exposures has become one of my favorite shooting techniques, especially for a scene that has water. Securing your camera to a tripod and opening up the shutter for an extended period has a softening effect on images that I find magical. I use long exposures for night scenes pretty regularly and this can be done without the use of a filter. Opening your camera's shutter for ten minutes during the day however will result in an image that is catastrophically over-exposed, so you need to darken things up a bit. This is where filters come in. By mounting a dark filter (or even a series of them) to the lens, long exposures can be achieved, even when the sun is out. The stationary objects in the image will be essentially unaffected but the moving elements such as water surfaces, clouds, etc. take on a much softer look that can change the entire feel of a scene.