It sounds as an obvious thing: you should focus on the subject of the photo. But sometimes you can choose an original solution by focusing on some ornaments of the photo (for instance, branches in the foreground, a thing that I like a lot because of the patterns they create) and letting the real subject a bit blurred in the background. Contrast and compare the following two photos to decide if you like the idea.

For the idea to work well, the foreground must not be too much distracting. I believe that in the previous photos there is too much foliage, so I found an acceptable solution as shown below, giving more room to the castle and choosing naked branches.