Last rung we proved the position carries meaning. Now: how do you actually use that on purpose? It comes down to three decisions you make every single time, whether you notice or not.
Move One: Eye Level
First, how high are your eyes? This is the same horizon from linear perspective, now used for feeling. Put the camera at the subject's eye level and you meet them as an equal — calm, honest, level. Drop below and they loom above you. Rise above and they shrink beneath you. Before you've chosen anything else, eye level has set the temperature of the whole shot.
Move Two: Framing
Second, what's in, and what's out? A frame is a fence — everything inside it is the story, and everything you crop away stops existing for the viewer. Include the whole crowd and your subject is one face among many; crop tight to just their hands and suddenly those hands are the entire world. Framing isn't decoration. It's you deciding what the viewer is allowed to know.
Move Three: the Rule of Thirds
Third, where in the frame does the important thing sit? Here's the trick photographers and painters lean on. Imagine two lines slicing the frame into three across, and two slicing it into three down — a noughts-and-crosses grid. Place your subject on one of those lines, or right where two of them cross, and the picture feels alive and balanced. Plonk it dead-centre and it goes oddly stiff and boring; shove it into a corner and it feels lost.
The four crossing points are sometimes called the "sweet spots" — the eye drifts to them naturally. In the toy, drag the subject and feel the interest meter respond: highest near a crossing point, decent along a line, flat and dull in the dead centre. Your eye already knew this. The grid just makes the knowing visible.