The truth is, I should have started the blog with this article. After choosing a camera (this a huge subject too!), once you start taking photos and before considering lighting, exposure, noise and other settings, you should take good care of composition.
There are some rules (never call them rules because from definition art is free from rules) that make your pictures better, depending on the photography type.
Rule of Thirds
This rule applies for everything: landscape, macro and portraits, but exception would be the classic portrait. This means that instead of placing the subject (main focus of interest) in the centre of the frame put it on an intersection of the thirds. For me it is much simple to consider this mind drawing where my subject is placed either in point 1 or 2 or 3 or 4:
Sometimes cropping a subject to make the viewer focus on some specific detail is an extremely good idea. But other times, when it’s not about details, it’s good to have the entire subject inside the picture and don’t take a shoot as if the subject is just about to leave, but rather just about to come if it is not standing. If you are in hurry or not so sure about what you want and you also got a high megapixel camera, you can afford thinking about cropping after shooting in the post-editing process. Otherwise, get closer and if getting closer will scare away your subject (hehe) then use your zoom.
Even if the Earth is not plane, we are walking on a plane land. Therefore, if the pictures are meant to reflect reality, just keep the horizontal and vertical the way you see it with the eyes. The most common example of the placement of the horizon line is in landscape photography. Sometimes, however, the pictures are not meant to depict reality and just by questioning your imagination you’ll be able to find situations (frequent in architecture photography) when shapes look more interesting deformed.
For an unknown reason, this is my favorite rule. No matter of what or who your subject is, imagine a diagonal (I’ve been once told that down left – up right is better than up left – down right because it appears like going up instead of going down but I wouldn’t care too much about that). This is very easy if you have a road or a river or some other natural line, and harder if don’t have anything alike.
Most people keep the camera at the level of their eye but this is just the classic way of shooting. The perspective can change quite drastically, especially with wider angled lenses. Sometimes the subject requires you to get down. I’m a short person so I ask people to take pictures of me that way because it makes me look taller. Pointing up-down is a quite more seen situation than pointing down-up. Some cameras come with rotating LCD-s and I find this quite useful: you don’t need to stretch yourself and the camera to get a down-up photo, you only rotate the LCD until it meets your eyes.
Even if your eye caught something that makes you say this is worth shooting, after a while, you or other people looking at the picture may spend minutes until realizing where in that photo is the thing! This is happening when shooting against a busy background with many elements and colors (ex: people on the street). Macro and product photography mostly deal with background problems: it should be something as simple as possible not to disturb the attention from the main (and only!) subject.
I say the main and only subject because: another rule in photography spokes that one subject is better than two and also better than none. You must definitely have a subject, which means you are not shooting without thinking of something, and, if you really like to catch more objects that are not related to each other, just take separate shots.
The subject pops out when its colors and/or tones are in contrast to the background and/or other elements of the picture. This adds to the simplicity and background rules.
A book I recommend on this subject is Master Composition Guide for Digital Photographers .
In addition to these you may consider natural framing.