Lots of runs of Cat-5e or Cat-6 from your tv/projector locations to you main equipment areas. You can run nearly any signal over Cat-5e/Cat-6 these days and the more runs you have the better, especially when thinking toward the future.
I like the recommendation of dual 14 ga runs as well.
Plan for how things will be when finished an work your way backward from there to best prepare from a wiring standpoint. Remember that extra wire runs are cheap now compared to a costly retro wiring job in the future.
I also recommend dedicated circuits for your HT lighting and dedicated circuits for your gear. 20A circuits (2) for your gear are usually my recommendation.