So you've checked out the good stuff and decided to take the plunge to Snow Leopard. Upgrading is mind-numbingly easy, but in case you wouldn't mind a little hand-holding, here's our quick and simple UltraNewb guide to upgrading from Leopard to Snow Leopard.
Prep Your Mac
If you haven't already, be sure to prep your Mac for the upgrade. In a nutshell, that means doing a little housekeeping (no need bringing old, unnecessary clutter into your shiny new upgrade), backing up data, and choosing your upgrade path. For our purposes, we're going to assume your upgrade path is a straight Leopard to Snow Leopard upgrade, though a clean install is always nice if you really want to get that fresh start feeling.
One thing to note: You'll need at least 5GB of free space to upgrade using the basic Leopard-to-Snow-Leopard upgrade path. If you don't have enough free space (my laptop didn't), try an application like GrandPerspective to identify large files you don't need and free up the necessary space.
Install Snow Leopard
This process is exceedingly simple, but as I said above, sometimes it's nice to watch the canary in the coal mine so you know what to expect. So, here goes:
1. Insert the Snow Leopard DVD: Just insert your Snow Leopard DVD, open it up, and double-click Install Mac OS X.
2. Click Continue and Get Installing: At the first screen, hit Continue. You'll see a licence agreement; read away and agree to continue.
3. Choose Your Install Drive: The Snow Leopard install disc will automatically determine your install drive if it's obvious, but if it's not—or if you don't want to install to the drive it automatically selected—hit the Show All Disks button to select a different install drive. Otherwise, just click Install.
4. Enter Your Password: This is the point of no return. Assuming you're all prepped, just enter your password and take the plunge to Snow Leopard.
5. Wait At this point, you're pretty much done. (We told you it was easy.) Grab a cold drink, put on some music, and wait. The installation will start as soon as you enter your password. On my computer, the install process went on for about 15 minutes, then restarted, then continued for another 50-odd minutes. (It hung for at least 10 minutes when it said "Less than a minute" remaining, but I've got an old-ish MacBook Pro, so yours may be a bit faster.)
6. Enjoy Snow Leopard: When it completes, your computer should restart once more. When it starts up, you should be greeted with Snow Leopard's intro video (it's actually the same welcome video as you saw when you upgraded to Leopard, which doesn't help Apple's case against people who consider Snow Leopard little more than a service pack). You'll then see the setup assistant. If you've taken the straight upgrade path, chances are you don't need this at all (I cancelled rather than sit through another MobileMe pimp session.) You can always run the Migration Assistant later if you need to. (/Applications/Utilities/Migration Assistant.app).
Now that you've upgraded and had a chance to spend a little time poking around, let's hear what you think about the cold kitty in the comments.