It depends on the tv and the pc, what output connections there are on the pc and what inputs on the tv.
For instance on a fairly new pc and tv you could have a hdmi connection from your video card to the tv, which is the easiest to connect.
4. Turn on your TV. Use your television remote to change the input to "S-Video" or "S-VHS." Typically, most remotes allow you to cycle through inputs by pressing a button labeled "Video" or "Input."
5. Turn on the computer. If you do not have any other monitors plugged into the PC, Vista will automatically detect the new screen and project onto it. If, however, you want to have the TV hooked up to your Vista PC alongside of a conventional monitor, you will be presented with display options upon start up. Of these options, the one you need to pay attention to is the desktop extension option; you can opt to check or uncheck this display option. Check the box if you want to have different applications running on each screen; uncheck the option if want to duplicate the same screen images on each monitor. After your initial selection, you can change this setting later by right-clicking on the desktop, clicking "Personalize," and then selecting "Display Settings."