"Anyone else have any non-obvious tips like that, that work great?"
I like making fairly "dense" scenes with  a lot of meshes and textures.  Used these tips on most of the renders in my gallery.
Couple of my favorite tips;
When making a big scene. It's helpful if you assemble it in smaller pieces - groups of figures, landscape, etc.  If there's a lot of figures, individual figures or small groups can be exported as meshes, and then imported as static props. - cuts 'WAY down on resources.  Then as the scene gets larger, save subsets of the scene as PZ3s.  Once your happy with all the individual components, just re-import (file->import) all the individual PZ3s into one large scene.  Then just double-check the lights haven't gone wonky (happens sometimes when importing PZ3s into PZ3s), save a master PZ3, and hit Render.