First, download the SteamInstall.msi from here and save it to your home directory or some Downloads directory.
If you do not have Wine, or do not have Jack or OpenGL, you will need to emerge it first. Type: USE="jack oss opengl" emerge -av steam in Konsole or your favourite terminal program.
Now, press Alt+F2 and type in winecfg to get to the Wine config. On the Applications tab, make sure the Operating System is set to Windows XP. Now click the Graphics tab. I don't know if this is required, but on my computer i had to select "None" on the Vertex Shader Support and untick Allow Pixel Shader. If that doesn't work, go back and tick it and select Hardware. Then goto the Audio tab and select Jack as the audio driver. After this is done, click OK.
Steam uses the font Tohoma. If you do not have this font, you will not be able to see any labels or anything on steam. I tried running it like this, trust me, its not fun. So I had to mount my Windows partition, go in and find the font. But lucky for you, I have uploaded it here. Save this file to your fonts folder on Wine, it should be ~/.wine/drive_c/windows/fonts.
Now to start the install, type wine msiexec /i /home/<your username>/downloads/SteamInstall.msi (be sure to replace the path with where you downloaded steam too. If you are not sure, try ~/SteamInstall.msi). Just follow the installation process like it was on Windows.
Now after the install is done, it will run Steam on its own. Close this. Then run steam again by typing: WINEDEBUG="fixme-all" wine C:/Program\ Files/Steam/Steam.exe.
You may get a dialog asking you to install Gecko. If you do, just click Install, it should only take a minute. File:Http://www.rapidrip.ca/steam/steamgecko.png
Now Steam should be up and running, simply install your games and start playing. I recommend running games at 800x600 even if you used to use higher resolution in games in Windows, and set fps_max to your refresh rate like Media:http://www.rapidrip.ca/steam/cs1.6.pngFile:Http://www.rapidrip.ca/steam/cs1.6 thumb.png. If your panels seem to stay on top of the game, just disable Beryl by clicking the Beryl icon in your system tray and click Select Window Manager|KWin (KDE Window Manager) you can change this back to Beryl when you are done pwning n00bs.
And finally, have fun :-)