In geographic information, this question comes with a big fat “wait a minute”. If you are representing a curvy/round/spherical object in a 2D plane, you will need to be aware of distortions (***), thus need to chose your projection wisely. Spatial referencing will fix issues of location and for measurements based on underlying data, unify all data regarding that location -- but if there is a projection (and often there is, as we live in a 3D world and study 3D structures of the macro or micro universe; yet we draw things in 2D, in fact we are often encourage to do so (***)) -- there will be distortions. This spatial coordinate system you chose will also reflect when, for example, you want to add photo-textures (imagine draping aerial images over the terrain) and you might get visual artifacts from this. While sometimes we might want to prioritize the geometry and accept some trade-off in visualizations, in some cases we might very well chose the opposite. This is linked to the previous item (#8), we need to assess our accuracy needs.
It is also interesting to think about scale -- and not only geometric scale -- it can be temporal (animations, interactive visualizations, time lapses) or attribute (multi-variate, high-dimensional data). It is good to consider if you can communicate what needs to be communicated with a single scale, or if the visualizations should be prepared for multiple scales. The amount of detail you will chose to include will be different at different scales. In cartography, the concept generalization (which is basically a set of visual operations about what to show, emphasize, group ..) is tightly coupled with scale, because scale determines what kind of “screen estate” we have (***). If you design for multiple scales, be aware of the transitions between them, and again, consider the users and the tasks to make a conscious decision if it should be interactively designed or whether to show various scales side by side.