1. If you really really depend on your Mac, maybe wait a couple of days? What folks in the biz call ".0 releases" are famous for delighting many AND completely screwing up others. As they say, "pioneers get arrows in their backs." Why not wait and let the bold go where no one's gone before, and read a few reports about how it went for them before you offer up your fine running machine to the gods of software upgrades?
If you decide to ignore that, my wisest advice, then how about this? Backup, backup, backup and utilize Utilities!
2. Back up your whole hard drive. That shouldn't be a big deal because you do that all the time, right? If not, get in the habit. Between low prices on hard drives, and great software including the built in Time Machine and the free Carbon Copy Cloner ("CCC"), you have no excuse not to, and a few million reasons (counted in megabytes!) that you must. Even if you run TimeMachine regularly, there's nothing like the bootable, complete hard drive clone that CCC will create for you when it comes to disaster recovery. Recovering your system from TimeMachine is certainly doable. Just don't count on doing anything else for hours - maybe days - if that's what you end up having to do!
3. Run Disk Utility. Make sure your hard drive reports no errors and that your disk permissions are OK. If Disk Utility finds any errors, have it fix them and run it again until it reports a clean system.
4. If you've moved any Apple installed software, move it back or reinstall it. Many times, Apple likes to see its stuff where it put it when it's making upgrades.
5. Run Cocktail, Onyx and DiskWarrior if you have them. Now is the time to run any utility you have that can help insure that your hard drive and your system software are in order.
6. Back up again now that everything is perfect. I'm not kidding.
7. Think again about my first piece of advice. I'm serious.
8. Good luck.
9. Let me know how it went!
