You need to know who your readers are. Without this information, you will have a hard time reaching out to them. Remember that in writing you need to know your readers in order to engage them and keep bringing them back to read your blog and to your website.
If you write about pets and your pet is a dog. Your audience is more than likely be dog owners, breeders, or people who are interested in getting a dog as a pet. This is a good way for them to get information about dogs and their care.
Maybe you write about the world you created and you wrote a book. A good marketing plan is to have the blog go into more detail, or expand in your own world. Look at Star Wars.
A poetry book is fun to write about. Go into detail on why you wrote the poems. The audience makes your blog a success, make sure you get the right audience.