This is just a quicky!
Sometimes you take a picture and the lights or the sun in the picture form a star like shape. How does that happen? Well my understanding of it is that if you use a very narrow aperture (f22 or higher) then the light "sprays" through the small gap caused by the blades of the lens. It's almost like the opposite of what you are trying to get with bokeh and a wide aperture (which gives you blurry round lights in the background of photos).
Anyway, this shot was taken at 15mm f20 1/125th sec. The high f-number causes a narrow aperture and the light from the sun sprays out like a star. It's quite a nice effect but bear in mind the following...
1. Narrow aperture requires bright light or a tripod (for slower shutter speeds)
2. Depth of field lost with high f-numbers
3. Looking through the view finder at the sun is just stupid. Use Live View instead.
You can see here I've used some of the dappling from the trees to reduce the light coming from the sun or else I would have ended up with completely silhouetted trees and hand.
Go and have a shot just now. Try it on some spot lights first at f 5.6 and then f20 and see the difference.