As always a fine list, but a few quibbles:

4. Write an outline of every scene in detail before you begin writing the actual screenplay.
This is the most efficient way to write, but some people do better writing the outline after a draft or two. Sometimes the scenic route is more profitable than the shortcut. Sure, the outline-free draft will be garbage, but all early drafts are, regardless of how they’re planned. The downside of a thorough outline is that it tends to fix a story’s trajectory before a writer has explored enough possibilities. The downside of an exploratory draft is that you’ll need more drafts before reaching your goal.

7. Script listing sites are similarly a waste of time and money.
They usually are. From what I’ve heard, Inktip generates a good deal of interest, but it’s often from bottom feeders. To do well on The Blacklist, a script has to be really, really good (no guarantee, even then). Most writers submit to listing sites before their script is good enough. The worst sites are the ones that promise to send a script out to hundreds (thousands) of producers. These blasts just end up in the spam folder. I have yet to hear of anyone succeeding as the result of an online or in-person pitch fest, but maybe they work. Certainly even an honest one wouldn’t help if the script isn’t first-rate. You get a bigger bang for your buck by attending local film festivals and networking with real producers / directors.

10. If you want to be a screenwriter, you need to write lots and lots of screenplays.
Even then, you’re not likely to write a spec script that gets filmed. The spec may be optioned or die in development hell. The more likely outcome is that a really, really good script (handful of scripts actually) will garner a writing assignment. And there’s an ice cube’s chance that the assignment will be a major film from a major studio. But you build a portfolio of successful assignments and maybe, maybe, maybe you’ll have the leverage to sell a spec — if it’s really really really good.