Composition: The Subject
Make sure you know exactly what it is you are photographing, i.e. have a clearly defined subject. For example, if you are photographing a person and you are not interested in what's happening in the background, compose the photo accordingly (i.e. zoom in on them or get closer).
Likewise, if you are photographing flowers, wide shots are fine but you should also try getting up close and making a feature of an individual flower.
Don't have unnecessary empty or useless space in the photo (e.g. lots of sky if the subject is on the ground). In some cases you may have a good reason for including empty space — the rule is to leave out empty space which serves no purpose. If it adds to the effect of the composition, that's fine.
In some cases the subject is simply a scene or a landscape. You don't necessarily need a person or object to be the subject — it can be anything at all. The point is to be aware of what it is you are trying to capture, and how you can best compose the photo to achieve this.
Next Page: Overall Framing