You should read your favorite blogs’ editorial calendars and media kits! They’re available online.
WordPress has a built-in editorial calendar plugin, and it’s free to use.
Example from the pros: Editorial Calendar for 2013 from Sunset Magazine
Free download alert! The blog post planner and calendar
Squarespace users should check out their free calendar plugin for planning posts.
Check out Chris' class on making your own editorial calendar work for you later this month.