Just have the PSU plugged into the wall but the wall switch not on, thats then grounded to your houses earth. Then just touch a bare metal bit of the PSU everynow and again just to earth yourself. I also tend to wear cotton when building PCs, so a pair of jeans and a cotton tshirt. Also ignore the people who say they've never had a problem and don't do anything, 99.9% of the times thats probably fine, but having been one of the 0.1% who has buggered sometyhing with static its worth a couple of simple precautions.
E-I