There are a few rules that have to be considered when it comes to the Composition of a shot. You have to think about the Simplicity of the shot, the Rule of thirds, lines, balance, framing and avoiding mergers.
When it come to taking a shot you have to consider what it is in the shot you are focusing on. Taking a shot of a something basic such as a daisy allow the viewer to only focus on the one item. This shows a simplistic composition.
Lines make the viewer look into the picture more. Horizontal lines give a calming look to the image and the diagonal lines on the tracks give a dynamic look to the image.
Balance gives an impression of equality to the image
Framing gives a look through something to focus on the item.
It's important to avoid mergers in photography in the image below you can see the background distracts you from focusing on the man.