1: Create Your Brand - as any social media 'expert' will tell you, your author name is a Brand in its own right, with all its associated reputation, knowledge, experience and expertise. Choose an ID that's distinctive and consistent, secure your profiles across Twitter, Facebook, Instagram, Goodreads, WordPress (insert your own here) and as many other sites as you think you can manage, and/or have the skill and the time to use.
Ecko Endgame
2: Be Visible - once you have these pages, use them. Your Brand should be more than just your writing. Your profiles are there to tell people not only who you are, what you like, and how you feel. Make friends, talk to people, share your thoughts and opinions and moments. Above all, don't worry about the numbers. It doesn't matter how many followers you have or how many hearts Twitter has just given you, if you can talk to people and build your community, then you're doing it right.
3: Be Real - your online persona is extremely visible and frequently the first/only part of you that people can see. Don't fake it. Be yourself, and let it develop organically. Have fun. Have energy. Find your own level and make your friendships genuine. Don't be afraid to have bad days, and to talk about them. People will respond to you, and to your writing, a lot better if you're a real person.
4: Build a Platform - your blog page is your Home Base, the cetre of your Social Media Venn Diagram. Use it to talk about your writing process, your days out, your book, your garden fence falling down. Science discoveries that interest you, movie releases, the latest in shoes. Talk about your community and the events that make it happen. Also, if you feel strongly about something, it makes a far, far better soap box than losing it and ranting on Twitter - go for the win with the structured argument, rather than frothing. And never forget - anything you put online can come back and bite you!
5: Sense of Humour - make sure you have one. Don't forget where you left it.
6: Support The Community - the genre fiction writership in the UK is very much an extended family, and like all communities, it's about communication. Answer people, talk to them, show an interest in their hobbies and jokes and cat pictures. Make friends and then. When that book finally comes out, people will support you as you have supported them. Seriously, this stuff isn't rocket science.
7: Find/Share Cool Stuff - writing requires research. Sometimes it requires an awful lot of research. And sometimes, your community of friends on Twitter has answers and insights that can help you. Ask questions, explore other people's links and pictures - Social Media can be a source for all sorts of amazing inspiration. And don't forget to give answers, as well as ask questions.
8: Don't Feed The Trolls. Seriously. Just don't.
9: Say Thank You - if you're a published author, you have a team behind you that work very hard. Editors, cover artists, publicists, bookstores, bloggers, supporters, readers, and, if you're lucky, fans. If you're self-published, you have fanbase and readership and support network that all help to bring your books to the fore. Whatever your book sales, all these people have worked to make them happen and Social Media is a great place to say 'Thank You'.
10: Indulge in Self-Promotion - yes, you are allowed. Just don't overdo it.