Our vision is an amazing thing. Our sight is an irreducible complexity. Our field of vision has a center, and our mind assesses what we see and tells our eyes to scan and find the irregular and the different.
A photograph has a center as well. That is why usually a more pleasing photo, a more attractive photo does not put the "subject" in the center or divide the photo horizontally and/or vertically in half. A photo needs to have the ability to draw our eyes away from its center and stimulate our minds to want to scan the photo - assessing it, usually from left to right, just as we read words on a page or screen.
Using the rule of thirds - the Golden Ratio
When looking through your viewfinder or your LCD screen, divide the image in thirds vertically and horizontally. Imagine the dividing lines and place the objects of interest at the intersection of those imaginary lines. Put horizontal lines, such as horizons, on the upper or lower line - not across the middle of you photo. Put vertical lines that go from top to bottom on the imaginary 1/3 vertical lines as well. This effectively divides your photo into thirds rather than halves. With this in mind, you will see an improvement in the composition of your photographs.