Just wondering what the rule of thumb is for a safe distance to run RCA cables between my equipment?

In the end I suppose all that matters is if you can hear any hum or ground loop stuff audibly, right?

I have to hook up cables (RCA) between my deck, my computers, and my mixer. Each run will be anywhere from about six feet to as much as about twelve feet.

Obviously one would want to not run these cables near any potential power wires, transformers, other equipment, etc. that might be causing cross-over static, hum, distortion.

Are there any other words of wisdom I should know about?