- Clear your cache - Will save you some database conflicts and errors. Yes, it will affect the load time of all your specific character's data for a short time (mainly for tradeskills) but it's to be expected and you don't want to clear your whole WTF folder after a few hours of hair-pulling.
- Clear your auctioneer data - Time to clean up a bit of data, don't you think ? "/auc cleardata ALL" I believe is the right command line.
- Update your addons - Well duh, right ? Still, check often before and after the patch launch.
- Follow gold-makers on Twitter - Link to Power Word: Gold's Gold Blogging Directory - all Twitter info is posted there for everyone - There are more wonderful and helpful people out there, but you'll have to find them. Seriously, some very helpful tips (almost) in real-time can make you some extra gold that is only available on Patch Day.
- Don't panic/Don't get cocky, kid - Remember to breathe and to check the posting and canceling fees if you're going to go in an all-out undercutting war with other profiteers.
People have been saving their gold for this day/week - you just have to set the right price at the right time.