try keeping your mesh setting as low as possible. Other than that i can't really tell you anything without more specifics on what you are trying to model and what level of detail you are after.

Also, maybe a new computer?

save small so the saved file has no mesh in it but it will take more time to open when it regenerates that underlying mesh

having the size of the unused saved file smaller for HD space is the issue or keeping the model less 'expensive/complex' so you can work on a older PC is?

MAXIMIZE your RAM

rectangles, right angles

How does a right angle save space?

Saving small will make smaller file sizes on your drive, but it will not speed up rendering, which it seems is the issue.

I'd lower the mesh setting as FOG suggests. And if it is a big scene, try reducing the model to individual models of individual views. That is if you are doing a close up of a space, delete all the unseen parts of the model.

less wacky geometry, less data.

but seriously, it's alwasy a good idea to keep your layers and blocks nice and clean. purge constantly. check for redundant geometry (SelDup)

Ah I see what you mean...

Some render engines slow down when geometry is way off the screen. Not sure how, but be advised.

sped up rendering? Vray

not a huge help unless your model came from multiple files with blocks, extra layers, etc - but PURGE is always nice for simplifying as well