Preventing ESD with an anti-static wrap?

Hey guys, I've run into some great confusion about ESD. Half of the sources on the web seem to be saying that you should have the PSU kettle lead plugged into the mains and into the PSU, but not turned on, wheras the other half seem to be saying the kettle lead shouldn't be plugged in at all. Between these two options, which is the best for my components in the sense that I won't fry half of them?
Thanks for any replies
SpartanHedgey 

There are a few good methods

  1. Don't work on carpet
  2. Touch a peice of metal on the case about every 10 minutes or so
  3. use an anti static mat
  4. use ESD strap

Having the power supply plugged into the wall turned off can possibly result in a shock if you don't do things right. Go with one of those 4 options

What I usually do is unplug my power supply, take the side of the case off, and attack the wrist strap's alligator clip to some metal part of the case. Did it with my most recent build and its working fine. I usually make sure that everything is unplugged from the computer like the monitor, the mice/keyboard, etc, just to be safe.

Thanks for the response guys, it seems I have nothing to fear in terms of my parts
being fried my ESD unless my Dad touched some of them whilst I was out of the room. 
He seems quite ignorant to the whole idea of part breaking just by touching them :C  

Having the PSU plugged in means there is a connection to ground through your mains, so you can then ground you're EDS strap by connecting it to exposed metal on you case and not build up any charge.

Grounding yourself is the key here......just touching your unplugged PSU or case when its not grounded will not prevent you from building up a static charge. 

If you don't have a EDS strap, Ground yourself by touching a exposed pipe on a radiator or check if your S bends on your sinks are metal and grounded.