use spot light where possible. turn off shadows where possible. delete history where possible. do not render an image plan where possible.., if you can composite it in your compositor (After effects for example) composite it.., dont render a static image plan (this is just something that came across, not THE golden rule).

do not create elements for the sake of it you will not see in the final render.

get a bigger prosessor (I just did for the same reason, plus a near whole re-buld of the pC, power supply, graphics card, mobo, its alll still sittting in a box next to me.., but it will soon be purring)

keep your scene light but thats experiance.