According to Consumer Reports, you should clean your TV with a dry, soft microfiber towel. Most televisions are flat screens, so be gentle. You can then use a can of compressed air to remove any dust that's in the vents.
If your TV is mounted on the wall, you can still get the screen cleaned. Simply grab a step ladder and carefully wipe it down with a microfiber towel. Don't forget to also wipe down the remote control!