Writing is to entertainment what technology is to science.
That is, start writing and keep writing. Then, get some friends together and direct a scene. There are tons of aspiring actors who will work with you for lunch. Cameras are cheap, editing software is on every street corner. There is no excuse to not do it... except to admit you are either not that interested, or you're just lazy.
Think it takes more knowledge? You're wrong. I went to USC, and all I'm sure of is that the money would have been better spent just taking a camera and doing it myself. "But you made connections at USC!" people tell me. Wrong again. And nowadays, you'll find more friends dedicated to filmmaking on Facebook than at USC.
Maybe my response shouldn't be "just do it." Maybe I should say "just try it." And once you've tried it and realized that it can be done... then, just do it.