The rule of thirds will help your photos have a more polished look.  It will also help draw your eye to your subject.  What is the rule of thirds?  Take a photo and divide it into nine equal parts, with two horizontal and two vertical lines running through the photo.  You want your focal point to be at an intersection of two of those lines.  If it is a head shot you want the eyes on one of the lines.  Ideally you want one eye to be where to lines intersect.  Here is the same photo the first one is after I edited and applied the rule of thirds.  The second is straight out of camera (SOOC) without the rule of thirds.  She is a cutie in both images, but the first looks quite a bit more polished an artistic.

Rule of Thirds Rule of Thirds

How do you apply the rule of thirds?  Most editing software has a cropping function.  I use Photoshop, but I know Elements, Lightroom, and Aperture all also offer this feature. Within the menu options you can choose to have the rule of third lines show up while using the cropping function.  Now that I have taught you how to follow the rule of thirds I am going to tell you not to always follow the rules!  It would be boring if you followed the same format every time.  However, if you take a photo and it is good but needs a little something try the rule of thirds.  Or if you are trying to make something or someone the focal point this rule will be invaluable.