Here's a cool trick you can try out with your SLR camera. All you need is a large aperture lens (ex: 50mm / F1.8) and a sheet of opaque paper or cardboard. The out-of-focus dots that you see in the image are known as "Bokeh," a term which is derived from the Japanese word meaning "blur."
1) Create a fake lens hood with the paperboard by cutting out a hole in the shape of your choice.
2) Place the hood over the lens and see how it looks through the viewfinder.
3) Set your camera to its lowest aperture value or bulb exposure. Have fun!