It doesn't really matter, the risk of static shock is really minimal. If you are in an environment where there is a risk (eg you have carpet and you are wearing socks) just touch something metal that is grounded before you start (toaster, lamp, taps in your kitchen or bathroom, etc). Don't build your PC on carpet, use a table or some hard floors.
It's really not a big deal, I know people who have built even on carpet and never shocked. I mean, you probably know better than us if your house tends to cause you to build up static electricity :P