Using frames is another useful compositional technique. Frames create structure and shape in your image, this makes it look more interesting and focuses the eye of thew view on the main subject of your photo inside the frame.
Look for frames and arches created by buildings.
Or be more creative by using a structure in the foreground to create a more abstract frame.
Another useful compositional technique is called leading lines.
Leading lines are lines that take your eye on a path through the photo. Look for anything in a scene that can be used to create a leading line. Curved lines taking your eye to a point or subject in the distance work well.
Leading lines are good in photos because they encourage the eye of the viewer move through the photo along the line. By making someone look along the line it means that you have engaged them in the photo, which means they will spend longer looking at it, and will find it more interesting.