Audience quest: Pay attention to what your audience is asking and give them what they are looking for in your blog. Whether it is content or questions, make it interesting.
Series of articles - Create a series of articles on your blog if the subject you choose to talk about is an extensive one.
Post Ideas: At times you will just run out of ideas for post not sure what to do. use google and apps like Evernote to note down all that ticks in your mind. Something will surely turn into a new post.