Twitter is worth it if you like tweeting. Same is true of Facebook. Or Pinterest. Nothing wrong with having a social presence.
Vera Caspary wrote thrillers - but not like any other author of her time, male or female. Her specialty was a specific type that she pioneered - the psycho thriller.
There's almost no author alive who isn't weathering the tumultuous changes in the publishing industry.
You shouldn't talk about yourself all the time - most of us aren't for sale. Our books are. Talk about them. It's not a question of whether or not you're fascinating on a personal level - it's that your trivia and trials might not have any connection to the tone, tenor and sense of your books.
Don't spend more than 10% of your marketing/PR budget on a trailer. Trailers have to be marketed, too. So, far too many authors wind up marketing their trailers instead of their books.
Don't add people to your subscriber list just because they once wrote you a note. Or once answered a note you wrote to them. Don't put your address book into your newsletter database. Let your readers sign up.
