Having just looked at how to market your blog, what should you actually write about in this blog?
There's only so much you can blog about your book when it's not imminently due out or just released. Things like "I wrote 5000 words today!" aren't really blog-worthy, although they may be great for Twitter or Facebook. And unless you've stacked up books to release in succession, you're out of news-worthy events.
There are a couple of different routes to take to write a blog, but the important thing is to commit to it: there's no point in having one if you're only going to update sporadically. Write daily, twice a week, weekly – you decide, but commit to it.
So what do you write about?
Write about similar authors or events in the book world
Writing about and promoting other authors and their work might seem counter-intuitive at first, but if they write in a similar style to you, then their audience is your audience. If you write about them, let them know (assuming you are complimentary!). They'll share it with their followers, who will in turn come to see your site. Hopefully once they have read about the article about their author, they will also poke around on your site and find something they like. Readers don't usually just decide they will buy one book for the year, so while you might sell a book for your competitor, you might sell one for yourself as well.
If you write about other authors who write about other authors, chances are pretty good they will return the favor. And it gives you a reputation for enthusiasm about books and for being knowledgeable about your subject. Plus there's the added advantage that somebody searching for another may stumble on your article first.
Writing about events in the book world is great – local bookshops, book events, book fairs, library events. People are interested in these and will be searching for them. Be enthusiastic about your local independent bookshop and they will love you and it helps to have your local booksellers on side.
Write how-to guides
A bit harder, but this can help establish your reputation within the industry. A lot of aspiring authors are inexperienced so don't know what they are doing, and you can share with them the benefit of your own experience. This may not necessarily bring in book-buyers (although many authors are voracious readers as well), but the audience is huge and eager to share, building a base for your traffic.
Write about the process
Writing about the research that is going into your current book will pique interest in your next book and some readers will enjoy going along the journey with you. You could engage readers by asking for suggestions for names or feedback on scenarios – they'll enjoy reading something and thinking "that was my idea!"
The trouble with this is you may not have subject matter for a lot of blog posts, or at least not very frequent posts, which can lose you audience. If they're not expecting random posts, then they won't check in for them.
Write about your own life and experiences
Not the easiest option, but it can be rewarding if you do it right. It's difficult to interest people initially if you're unknown, but if you can write entertainingly (and usually lightly) about the trials and tribulations of your life, people will enjoy it. It can be a great outlet for creativity. However, it does involve opening up your life to the world at large and this is not everyone.
Alternatively, you could comment on world events and turn it into a more general blog rather than writing, but if you can tie it in to yourself or your work, so much the better.
Any of these are good options for how to organize your blog, and combining them can make a great blog. It may take some time to work out what is best for you and your audience, but the important thing is to stick at it!