You may have heard that the Rule of Thirds is the main photography rule to follow. Like all rules it can always be broken, however it provides a very useful guide to composition for beginners.
This is because people instinctually like to place subjects in the centre of photographs. However when the major elements of a photo (whether that is a subject or the horizon) are placed on the lines that divide an image into thirds, the results are more visually pleasing.
Why does this rule work? Good question. Most people will tell you "It just does", or talk about the "golden ratio" (which is a mathematical equation the rule of thirds is based on). My theory is that having the main subject off-centre forces the eye to wander and take in the rest of the image.
In this photo the position of the subjects draws focus to them and we also get a sense of the season and place they're in.
Many cameras allow for a grid to be displayed on the camera's screen for easy alignment. If you have this feature its a great way to get started. However, its easy to picture the grid in your mind's eye. Just estimate an imaginary line one third in from top, bottom, left or right.
Don't get obsessed over trying to place every subject on an intersecting point. Placing your subject along the third lines either horizontally or vertically, left or right, will have the same effect.