How do I get better at modeling data, not just storing it?

You can store data, that is the mechanical part, but modeling it well feels like a different thing, and it is. Storing asks where to put the data. Modeling asks what the data means and how its pieces truly relate. Feeling that gap is the first real step toward crossing it. Good modeling is less about the tool and more about understanding the real world the data describes. Before thinking about tables or structures, get clear on the actual things you are representing and how they connect: what belongs to what, what depends on what, what is one and what is many. When the model mirrors reality accurately, the storage almost designs itself. When it fights reality, everything downstream gets painful. One step: take something you are modeling and, before touching the structure, describe in plain words what the things are and how they relate to each other. Get that story right first. Modeling is mostly clear thinking about relationships, and that is a skill you can build deliberately, one honest model at a time.