Managing your focus depth
By the time you reach this tip I hope you are spending more time with your camera in Manual mode. This tip is going to teach you how to play with your aperture to get some really cool closeup shots and depending on your lens this will also give you another great tool to help the composition of your photos.
Find something small to practice with for this tutorial like a flower, your watch or ring, or even your grocery list. Set your aperture to the smallest setting that your lens will allow (hopefully it goes to 2.8 or you should really consider an upgrade) and take a photo of the object you've chosen. Try to pick your focus point in a place that you can remember so you can see the difference in the settings.
Now adjust your aperture to 4.0 and take the same photo. (Keep in mind that you may need to adjust your shutter speed to keep your exposure correct) Then take another photo at 8.0 and download your images so that you can really blow them up on your computer.
At first comparison you should instantly see that the focus is much more specific in the image that was captured at 2.8 and the focus gets more broad as your setting went up to 8.0. Do you have a favorite out of the three images? Chances are that the image at 2.8 adds more visual interest because of the specific focus point while the one at 8.0 allows you to see more details in the object.
How can you use this in your photos? Well there are many comon tools in photography and art in general to draw the eye to the main subject of an image and by using the aperture to put our main subject in sharp focus we can draw more attention to it while still showing a wider scene. For example if you wanted to take a photo of a couple dancing among a sea of other couples and you wanted them to be the only subject of the image you would shoot them at 2.8 which would make the other dancers go out of focus enough so that we would understand that they were there but our eyes would be drawn to the couple in focus.
For extreme closeups (typically using a macro lens) using a low aperture setting can really add to the effect of being close to an object. Of course if you were taking a photo of a mountain your aperture setting would not have the same effect because of the size of the subject. This is a fun trick to play with and will give you something else to make your photos a little more interesting than everyone else's.