This may help a lil bit..The grid here represents the rule of thirds.(I did it fast so grid is a lil off, but you get idea).
The red dots represent the 4 more main focal points in any image. Don't ask me why, it just is. As you see, the render dead center is off, and the text is way off. Even if your render isn't in the focal areas, you want something going on there. Although this is by no means a LAW, but it's basic composition and it helps put together images that are pleasing to the eye.