One fun technique to keep in mind when taking pictures is the bokeh. It comes from a Japanese word meaning blur or haze. The idea is to use your lens to cause parts of your picture to blur out artistically. Another strategy is to use the blur to highlight your subject matter which you will place in sharp focus.
The trick is to set your camera to manual mode or AV, "aperture priority," and then crank your aperture to the wider of the stops, say 2 or 1.8. That creates a very shallow field of focus. Everything closer to the camera than the field of focus will be blurred out and every thing behind it will as well. But as you can see, it really draws the eye to the subject.
This is especially handy when doing portrait photography. The aim there is to get the eyes as sharply in focus as possible. Then sometimes you can used the blurred out background to communicate something about the subject's environment while at the same time there is no doubt as to the focus of the picture.
Also you can use bokeh techniques to get some really cool effects. When I took this picture of the candles, I strung some Christmas lights up in the background. They are so far out of focus that the results are pretty dramatic. There are ways to play with this effect that I will approach some other day.