Thanks for bringing up YouTube. I didn't mention it because far fewer authors use it than social media like Facebook and Twitter, and it may require hiring a video editor and others if you lack the tech skills to do something that wouldn't embarrass you (which authors typically can't afford--they need "free").

But you're right. More and more authors are doing YouTube videos. And I suspect that even as I write these words, there are editors, agents, or writing coaches who are insisting to writers that they "have to" do YouTube videos. It puts such a burden on authors who aren't making enough money from their books to justify the expense!