Turntable background noise

I had a large amount of background noise coming from my turntable input. The pitch and volume changed when i picked up the tonearm and moved it over the record. When i switched to any other input speakers were quiet (volume up, no music playing).
My power conditioner was mounted directly underneath the shelf where the tt sat.  I ended up moving the power conditioner as far away as i could from the tt and i would say 90% of the background noise has been eliminated.  

How far away should a turntable be from amps and power conditioners?

Are there cartridges that are more suseptable to this type of interferance?

I have my ground connected to the phono preamp. Is there a better way to ground?  Should i make a tinfoil hat to put over my conditioner and amp?