I recently re-did my living room and ran new electrical, cat-5, phone and coax to the areas I was upgrading. From a new cabinet, I ran HDMI, structured cable (5 in 1), cat-5 and coax to the tv. i also ran speaker wire (UL approved for in wall) to the attic for ceiling mount speakers.
You really have to have an idea of your application and future needs. The cat-5 came in handy for my components that have network capabilities and u-verse comes into my living room via cat-5.