Well as far as workflow is concerned: when you want superfast viewport speeds in solid view, then work in Direct3D. Seriously, I have had 1.5 million poly scenes on my screen that scrolled and zoomed as if they are 10 polygon models. As fast as possible (100fps+).
In wireframe you're always almost pretty much screwed.
Furthermore I almost always keep everything hidden all the time, except for the object I am working on (except of course when you need other objects are reference). That way my viewport is always fast.
Use the render iterations option in your meshsmooth. I alsmot always have 2 iterations on any object, but only 1 in my viewport. Very handy if you ask me.
I also use selection sets, which is somewhat like layers, only a bit simpler and with less features, but I never understood layers until the beginning of this year, but I don't really feel like I need more than 10 selection sets anyways.
RAM wise: well high polygon counts + big ass textures (bitmaps!) is killer RAM wise, so try to avoid if possible. In scaneline you hardly ever run into trouble, but with Brazil for instance it's almost impossible to render big scenes on a 1GB RAM machine without getting memory errors. Praying sometimes helps, but then again it's Brazil...
Don't really optimize much for the rest, especially not RAM wise. If it doesn't work: get more RAM.