This one is pretty simple. You should arrange your compositions in triangles whenever that works. Triangles appear to be more dynamic than rectangles or circles and so people see them as more visually exciting and appealing. Point-down triangles appear more top-heavy and so can add some to the appearance of "wrongness" in a surrealistic composition, and point-up triangles appear more stable and so appear more visually appealing in a more conventional composition.
Probably for the same reason, odd numbers appear more visually appealing in a composition, although you can shoot four people in a composition and make it look more appealing if you arrange them in a triangle shape.
Lines and curves:
Serpentine shapes almost always seem more visually appealing than straight lines too, so if you have straight lines, have a good reason for them, like using them as leading lines. The most visually appealing