I've got a very large polygon land cover map (millions of polygons) over a large area. Our first try at serving the data through GeoServer WMS was not very successful due to the large amount of small polygons. So it was suggested to use scale specific styling (along with spatial indexes) to show only the larger polygons at a broader scale and refine as the user zooms in. This process of setting which polygons appears at each scale, based on polygon size, is a trial and error approach? Or are there rules that one could follow in order to identify which features to display depending on the scale?