I've been writing blogs like mad, but for other blogs as a guest. All part of my promotion campaign and fulfilling the very kind requests. Someone asked me, what do you write about? So I thought I'd pass on my ideas.
Obviously the point of doing guest blogs is to promote my upcoming release. But nobody wants to hear or read about that over and over again. It's necessary to find something that relates to the novel, but isn't a direct selling pitch. Thinking around the novel, there are always going to be points of general interest.
With historicals, it's easy enough to pick up areas of research and talk about those, which is what I've mostly done. But what if your novel is modern? Are there still points of interest you can fix on.
Think of it as you would a hook for your story. Is there something in the area of the setting? You may have had to research something about it, or about the type of buildings you're using, or the lifestyle of one of your characters. Use your research and talk around the theme, only bringing in your story where it's really relevant, and perhaps only once - twice at the most.
Is there a medical or physical problem involved with a character? Even the simplest things - an allergy, a sprained ankle - require some specifics about the problem, its treatment, how it incapacitates the character. Anything of bigger medical interest will have its own data you can plumb for your blog.
If you're doing something light, why not write about how you choose names, or how characters get their hair and eye colour, whether they arrive fully formed or appear gradually. This sort of writerly inside information is always of interest to the non-writer. Then it's easy enough to bring your current characters in and tell how they became who they are.
Thinking about it, there are endless possibilities that lead inevitably back to your novel under promotion. Covers are a good bet, and invite pics as well. Titles - fraught with interest! Readers would love to hear all the titles books didn't get called - even the bad ones. Awful howlers that got through copy edits galore. The horrible agony of getting a decent author pic. Having to rewrite half a book because you boobed.
People love to read about mistakes - it makes you human. Don't try to focus just on the good stuff. Life isn't all sweetness and light, and it warms the heart to know others are just as vulnerable as you are. On the other hand, don't play the sympathy vote with a dreadful sob story. If you're talking about the horrors of life, make it light. And then your lead character's difficulties in the current book are easily brought into play.
Remember - as a writer, you are already interesting. Talk about some aspect of your work, and you can't go wrong.