I am a registered photographer with Getty Images. Here are five simple, important rules, illustrated with photos I found on Google.
If you didn't know them before, they will instantly improve your photography.
1. Use the rule of thirds. Place the main lines of your photo along the lines shown here, and position the subject(s) at the points where the lines intersect. It's like harmony in music; it only works to create visual harmony.
2. Remove unwanted objects if they don't improve the image. Look at the entire scene before pressing the button, not just the subject.
3. For appealing portrait photos, use flat, matte lighting.
4. For appealing landscape photos, use the opposite, dramatic directional lighting.
5. Modern camera equipment and software are very forgiving of poorly exposed photos. However, they are not perfect. If you overexpose, you cannot correct it later. If you have to choose, you will always err on the side of underexposure.
Please excuse my poor German, I am not a native speaker.