In Ubuntu 12.10, launch Software Sources, click on the Additional Drivers tab and install the latest experimental drivers. You can skip this step if you are using Intel graphics.
2. Install the client
Head to Steam's website and download the 1.5MB .deb package. You can either double-click on the file and install it with Ubuntu's Software Centre, or install it from the terminal with sudo dpkg -i steam.deb. This will launch the graphical installer, which will then download the client.
3. Create an account
After installation, the Steam client will be docked in the Launcher. When you launch the client, it'll give you the option to create an account. If you already have one, enter your login credentials. In this case, since you are logging in from a different computer, Steam will send you an email with a confirmation code to authorise the new client.
4. Download games
That's it! You're now logged in to the Steam client. The Linux client doesn't look any different from the one available for Windows. The Linux tab in the Store section lists all the titles currently available for Linux. You can start by downloading the Team Fortress 2 game, which is available for free, and then purchase additional titles. Some titles also offer free playable demos.
5. Offline mode
Besides the multiplayer games, Steam also has some single-player titles that you can play offline. Steam will start in the offline mode if there is no internet connection available, or you can manually switch by heading to Steam > Go Offline from within the client. Before you can play the title offline, ensure you've activated the game by going online at least once after installation.
6. Connect to TV
Valve is also beta testing a new mode designed for using the Steam client on HDTVs. To switch to this mode, connect your computer to an HDTV, launch the Steam client and click the Big Picture button. Besides links to the Steam store, library and community, the mode has a web browser. It's designed to be navigated with a game controller, but also works with a mouse.