Scan your eye around the edge of the frame, check any small detail that protrudes in from the edge of the frame and ask if you want it in the frame, if it is to be part of the design of the image make it large and significant enough so as it works as part of the design. Small details like those arrowed in red can act more as a distraction.
Also make sure that verticals and horizontals like those arrowed in green like up with the edge of the frame.