I'm trying to make tips which are renderer independent. This tip would apply to a renderer which allowed you to mark a specific object as rendering as if it were illuminated, without actually placing lights in front of it, placing lights behind it or treating it as a light source. I believe there are several rendering engines which have this concept of "self illumination".
Of course, a television set, or a back lit sign, does provide illumination in the real world, but unless you are emphasizing this effect - such as a TV in a dark room - it may be easier to brighten up the TV screen without making it an actual light. (Many of my rendering tips are shortcuts to achieving an effect without replicating things perfectly. For example, (a stupid, extreme example), it your television set is a LED model, then you should place millions of LED lights - eash of a different color - to more perfectly emulate the way the television illunimates the rest of the scene)
How do you handle television screens currently?