Visit Each Blog Before You Query.
Read more than the one article that comes up when you Google a subject. Visit the blog and read several posts.And read the guest post guidelines if there are any. (This is really important!)
Also read the comments to see if that blog attracts people who really might be interested in your book. Leave a comment on a post you enjoy.
The best place to start querying is a blog you read regularly because you genuinely like it and have an interest in the topics it addresses. If you're a regular reader and commenter on a blog, you're much more likely to get a spot.
Guest blogging is a great way to introduce people to your book.