I'm on again, off again with Twitter. There's so much nasty and politics on Twitter that some days I can't stand to open it. I find Facebook to be useful at times but I think it's getting harder and harder to be heard there. I do blog about once per week. Don't know if it helps but I've made many contacts to organize my own blog tour.
Pinterest and Instagram are avenues I'd like to explore and I'd like to learn more about YouTube.
Honestly I'm convinced that social media doesn't help much for marketing books. You can't dazzle people with your colorful screenshots and slick trailers when the product you're pushing is black text on white paper, and there's a reason all those Lord of the Rings memes you see are subtitled movie screencaps instead of photos of the equivalent line in the book. Social media is a shouting contest, and writing is a silent medium.
In fact, one of my long-term marketing strategies is just to make a game that takes place in the same setting as my writing. It's not a surefire plan of course, but considering people buy Five Nights at Freddy's novels, don't knock the power of game lore and media overlap.