A common mistake when taking photos of people is to put their head centre in the image, this is not eye catching or flattering
Putting the person in the centre distracts from the surroundings, which are used to emphasis the person
Putting the person in the third of the image allows them to be seen, but not distract from the overall image, allowing context.
There are many 'rules' with composition - I pick the easiest ones to remember - but don't forget rules are guidelines or 'starting points', they can and should be broken at times. Here are some suggestions to think about.
The Rule of Thirds!
Basically imagine your image divided into 9 equal rectangles, the important aspects of the image should be on or close to the intersections.
The examples below (whilst not the most interesting shot) shows how different a scene can look given something in the foreground to add interest, It was a meadow in the evening, however by taking a step back to include the style adds more interest to the image.
The eye and leading lines
It is important to understand how the viewers eye moves around the image, the eye naturally follows lines as in the first image, you do not want lines leading out of the image taking the viewer away from your image. The 2nd image has a sense of depth and mystery, leading the viewer to want to look deeper, therefore maintaining their interest.