Now that we've had a little taste of what goes in to composing a pleasing image, there are a whole host of subtleties that can go a long way to making a good photo better. Hardly a complete list, but some of the factors that are involved are:
a horizontal composition tends to emphasize the breadth of a subject (good for landscapes)
a vertical composition tends to emphasize height
—angle of view
a wider angle of view adds depth and distance
a narrower angle of view creates the illusion of size
lighter objects tend to add a sense of depth (think of mountains...the farther away each range is, the lighter it appears)
—depth of field (the range of distances that are in focus)
large depth of field creates a feeling of distance and expanse
shallow depth of field aids in isolating the subject from the background (good for portraits)
The way to develop your skills in composing an image is to practice. Unlike the good old days of film, with digital cameras it doesn't cost anything to take a picture. So, there is no excuse not to take lots of photos to get into the practice of visualizing the final image before you press the shutter button. Your investment of an additional five seconds studying what you see in the viewfinder will pay off big dividends in the end.
I'm heading for France and Spain in a few days, and won't be posting to this blog for the next 3-4 weeks. So, you have lots of time to get out there and shoot something.