Hooking a computer up to a television set is a common practice. If you own a Mac, this setup can be easily accomplished. Thanks to the support for multiple displays included in both OS9 and OSX and the convenient hardware setups from Apple, most modern Macs are shipped with the ability to connect to a television right out of the box. The wires that you will need to make the connection will vary depending on both the type of Mac and the type of TV.
Determine the type of video connection that you will need to make between your Mac and your television. Look at the available ports on both devices to figure out what kind of wire you will need. Most modern analog televisions include a VGA port, and high definition sets generally have at least one HDMI and/or DVI port. Your Mac will likely include a VGA, a DVI/mini-DVI, and/or an HDMI port.
Decide if you want your Mac to output audio to the television. If not, your Mac will still play sound through its built-in speakers while it is hooked up to your television. However, some setups are better served with external audio output.
Connect the Mac to the television with both of your wires, starting with the video wire.
Set your television to the input to which you connected the Mac. For example, if you connected it to the HDMI port, switch the television screen to the HDMI input. Your Mac should recognize the television as a new display and begin outputting audio and video to it immediately. If it doesn't, open System Preferences (Apple > System Preferences...), click "Displays," and then click "Detect Displays."
Use OSX to set up the Mac's output mode. Go into the "Displays" panel using the process in step 3 and click the "Arrangement" tab. You should see two boxes in the middle of the window; a large blue box with a gray strip on top and a smaller blue box attached to it. By default, the large box with the gray strip represents your main screen (in this case, your Mac's display), while the smaller box represents your television. You can move these boxes around to switch the orientation of your screens as well as choose which screen will act as the "main" display (the one with the menu bar on it). You can also check "Mirror Displays" in the bottom left corner, which will make both screens show the same thing.