Practice
While it's possible to contrive guidelines for specific photographic situations—get down low while shooting kids, fill the frame when shooting portraits, etc.—as you've seen, the process of making a good photo requires a lot of decision making and a lot of choice and experimentation. Rather than learning specific rules for specific situations, it's better to learn what it feels like to see, what makes a good composition, and how your exposure settings affect your image. With these basic building blocks, you'll be able to go far beyond simple formulas for different situations. You'll be able to find your own solutions that better convey what you feel about a particular scene.
We can discuss all of these ideas and rules for hours, and the discussion can be very enjoyable and enlightening, but more than any lesson, more than any new piece of gear, more than any piece of postproduction software, the single thing that will do the most to improve your photography is practice.
You must practice seeing; practice composing; practice your understanding of the effects of exposure, camera position, and focal length; and practice with the controls of your XS so that you can quickly adjust and adapt to any situation without having to think too much about the camera. You want your focus to be on composition. Practice will make all of these things possible. So, get out and shoot as much as you can, and pay attention to what works and what doesn't.
Because your camera records your exposure ...