Rule of Thirds explained

The 'Rule of Thirds' (ROT) is quite a common and well-known part of photographic composition design and although some of you may have already heard the term mentioned, you may not be brave enough to admit that you know of it, but nothing about it.
The ROT is one of those tools that can really change the entire perspective of an image. The simple act of altering the position of your main focal point and subordinate points of interest in the frame can create added interest and give a novel professional touch to your photos and help you win prizes.
The ROT is about assuming, when you look through the viewfinder of your camera, or the viewing screen, that you see an imaginative grid in the shape of a 'naughts and crosses' game, with a vertical line 1/3 of the way in from the left and 1/3 in from the right and one horizontal line 1/3 up from the bottom and another 1/3 down from the top. Where on, or nearest one of these intersecting lines, you arrange to place your focal point or main point of interest. Not in the ‘dead’ centre.
If the photograph you are composing incorporates a wide horizon; a seascape or desert landscape, for instance, if you have a very interesting sky with a featureless land, give the sky prominence by allowing it 2/3 of the frame and the land the other 1/3. On the other hand, if the sky is plain blue or grey and holds no interest, allow the land 2/3 of the frame and the sky the other 1/3. All the time remembering to also keep your horizon line level.
If you are doing a portrait, you can fill the scene with the head and shoulders, but place the eyes, or at least the eye nearest the camera, on or near one of the upper ROT intersections. For example, if the head of the subject, be it a person, animal or bird, is facing toward your left, place the nearest eye to the camera on or near the right upper ROT intersection. This will provide space in the frame for the subject to look into. And as the eyes are the focal point, be sure to concentrate your focus on them. In this case, It will not matter if other parts of your subject are out of focus, the eyes are the focal point in any portrait and for them to be placed on one or near the ROT intersecting lines can really give your image great impact.
The benefits of using the ROT concept was first discovered and recognised by the great classic artists, long before photography was even thought of.
There are many other rules or guidelines for photographic competition and as with anything else, rules were made to be broken, but it is a good idea to find out about them, practice them and then make a conscious decision as to when, how and if you will apply them.
But in photographic competition, if it gets down to the wire, if you have followed the rules correctly, it might just get you over the line.