The best advice is to build a list that you can email out to when new posts are ready.
Social media is also helpful. You may wish to post older posts to Twitter on at least a weekly basis.
If you write good quality posts, readers will come to expect your posts each month and come looking for them.
As for the blog itself. You might consider writing summary posts (linking to older posts) which invite comments in answer to discussion points. You might also want to announce posts in advance so readers know that they are coming up.