Having an editorial calendar for your blog simplifies and brings discipline to the process of coming up with post topics. Taking it a step further, an SEO friendly editorial calendar simplifies and brings discipline to the process of writing blog posts that support your SEO strategy.
Here is a simplified version of an SEO friendly editorial calendar format that works really well for me.
This hypothetical blogger with an online golf equipment store has four categories he wants to blog about.
Blog Categories. The editorial calendar lists and repeats the category group over and over, so the blogger can systematically cycle through the categories.
Blog Topics. In the next column, we drill down to specific subject matter the blogger wants to talk about within each category. For example, in the broad "Golf Equipment" category, wide selection and high quality are his two most important sales points. The calendar allows the blogger to switch off between the two themes, always having a relevant "angle" for his post.
Keyword Phrase 1. This column displays the primary keywords for each post topic. The blogger will want to incorporate them into each post, particulary as anchor text pointing to the URLs that appear in the last column - more about that in a minute. You'll notice that the primary keyword phrases exactly match the Category labels in every case. This is not a must, but if you can do it, you'll enhance visibility for that search term.
Keyword Phrase 2. Now we display secondary keywords, which may be "long tail," or niche phrases that perhaps - but not necessarily - apply more specifically to the topic. For example, when the Golf Clubs topic is Drivers - "low price drivers" is selected. When the Golf Clubs topic is Sand Wedges, target phrase becomes "sand wedges on sale." Secondary phrases usually vary more than primary phrases from topic to topic.
Target URL. The overriding goal of this blog is to drive traffic to specific landing pages of the blogger's online store, where people can buy his stuff. Therefore, every blog post will contain links to a landing page, which will help that landing page rise to the top of the rankings for the selected search terms. We always want the store's home page to appear prominently in searches for "golf equipment" and "shop golfing", so the keyword emphasis and URL target for posts in the Golf Equipment category will remain constant. However, in other categories, the target URLs will vary to cover other landing pages, such as drill down product group pages and sale item pages.
You should add other columns to the spreadsheet for things like Publish Date and Author, but I hope this stripped down version gives you the gist of the idea. A little time spent on planning up front can make a world of difference in your SEO results.