Intentionally zoning your image
Imagine the frame you’re shooting to be overlain by a grid. That grid must not necessarily consist of squares, you can as well picture it being made from triangles and so on. Start off by finding the center of your image, which doesn’t have to be the very middle of the canvas. You make your own rules what you want to perceive as the center of the image, there.
Your grid does as well not have to be a boring, repetitive or even symmetrical grid. The shapes you’re imagining can be different sizes. Since that can be hard to imagine, I advise you to sketch that basic grid on paper. Doesn’t have to be clean, but the final arrangement of lines shall be aesthetic to your eye. Now, try to adapt the concept of your photograph to that grid.
This act can help you with finding out what might be missing in your image, where to place props or people, what is missing to create the absolute harmony or tension you want to achieve. As you’re trying to depict your rough idea on a small piece of paper, you are going to get an impression of the total effect of your idea and the picture you’re about to shoot.
This method was already being used by the old painting masters of the Renaissance, who put a lot of attention to aesthetic perfection and added a grid to their empty canvas to plan on where to paint which detail. A photograph is a painting too, technically; you’re painting with light.
Mirroring and rotational symmetry
Using similar shapes in similar sizes in your image is key to achieve even distribution of details and, therefore, harmony. For example, if your picture includes a rose somewhere towards the bottom left corner and it’s a background, a stylistic idea would be to include a rose in the top right corner of your image as well, so on the opposing side. The same thing works with colours you’re using.
An example for the effective use of visual rotational symmetry would be if, for example, when your frame includes an arm pointing to the left, you would use another detail pointing to the right on the opposing side of the canvas. This creates a visual balance of details. The human eye is automatically looking for similar details and symmetries.