Golden Rules for Cable & Power Cord Arrangement

I would like to know some of the Golden Rules for laying out my audio cable and my power cables.

As much as possible I try to keep my power cables away from my audio cables, but there are times when they run near each other or even cross over each other.

I've also seen photos of systems where the cables are strung between little feet to keep them off the floor. Does that help the sound or is it frivolous?

Thanks for your advice!