sudo sh amd-driver-installer-catalyst-12.10-x86.x86_64.run
AMD's installer will run to install and configure the AMD drivers, along with the Catalyst Control Center GPU management software. These may not automatically update, because you didn't get them from a Ubuntu PPA (there is one, but it's not always kept up-to-date, so we aren't using it), but an update option should be in the Catalyst Control Center that you can use to periodically check for new updates.
Reboot, and you're done. Phew! That's half the hard part over with.
Installing and Configuring Wine
Even if you're going to be playing mostly games that have been ported to Linux, Wine dramatically expands your horizons for gaming without Windows, so it's highly recommended that you install it.
It's easy to get, too; simply open a terminal and run the following commands:
sudo add-apt-repository ppa:ubuntu-wine/ppa
sudo apt-get update
sudo apt-get install wine1.5
sudo apt-get install winetricks
The system may ask you if it can install other packages; go ahead and say yes. Once this is done, it's time to get in the habit of using Ubuntu key shortcuts--press the Windows key on your keyboard (yes, it's ironic; there's a very, very small chance this key won't have the Windows logo on it, and Linux documentation refers to it as the "Super" key, so just go with it) and type "winetricks"; then press Enter. The Winetricks interface will open.
Winetricks is a little program installed alongside Wine that lets you quickly install necessary Windows libraries without needing to track them down and figure out whether you're supposed to be installing the version for Windows XP or the version for Windows 7 or any of that. Once it's opened, tick Select the default wineprefix, press OK and then Install a Windows DLL or component; press OK again.
For minimum headache, you'll want to select the following packages from the list:
- everything beginning with "d3dx"
- vcrun2005, vcrun2008, and vcrun2010
- xact, xact_jun2010, and xinput
- optionally dotnet3.5. Skip this for now, but remember it when you see the "Troubleshooting" section below.
After this, click OK, and everything will install; most of it will be in the background, but you may need to click through once or twice. Good news: With that done, the hard part is now over! On to the fun part: playing games.
Where to get games, how, and why
Option 1: The Humble Store and the Ubuntu Software Center
The Humble Bundle is a fairly recent development in the world of PC gaming that regularly packages multiple indie games into a pay-what-you-want "bundle" for use on Windows, Mac, or Linux. Since its inception, it's been almost singlehandedly responsible for more Linux ports than were available in the previous decade, and it's probably going to be your best source for games that run natively and are thus (almost) guaranteed to work. Check the Humble Bundle website periodically, and if you miss a bundle, know that you can always get the same games individually for full price from the Ubuntu Software Center (similar to Apple's App Store, it's installed automatically, and will be where you obtain all your software that doesn't come from external PPAs; nearly everything but the games is free).
Option 2: Steam
As I mentioned in the introduction, Steam is now (in beta) on Linux! This is really exciting, as it means that Linux is being taken seriously as a gaming platform, and as a result we might see far fewer headaches involving video drivers in the near future. That said, if you have Wine, there's currently very little reason to use the Linux version of Steam. The selection is currently very small, since they provide only games that have native Linux ports (many of which are indies from the Humble Bundle), and virtually every game that's been ported to Linux already worked in Wine.
For the time being, I'd recommend sticking to the Windows version of Steam, as it works flawlessly, and using the Linux version of Steam only if you really need an extra 5 or so frames per second in a game, since native ports will run faster by a (surprisingly) small degree. Alternatively, you could use Steam for Linux if you really want to support gaming on Linux (and don't mind constantly logging out of Wine Steam to run Native Steam and vice versa, since you can't be logged in two places at once) and/or you've waited several years after I've written this for more games to be ported over.