Internal Linking to your older posts is always recommended for all the Bloggers and this is the reasons we had previously recommended WordPress Plugins like Automatic Internal Tags Link Building & Auto Link to Keywords which are going to revive the old posts and give them a new life by making the bots to crawl them regularly and also increase their value by the number of backlinks to them. Its also useful to link to some of your recently visited articles with the title using which the visitors arrived to your blog. This is possible by displaying the Incoming Search Terms for the Articles either on the sidebar in the form of a Widget linking to the Top 5 Popular Searches or any place you select on your theme.
Download LJ Longtail SEO WordPress Plugin which can perform all the above listed tasks easily. Just install it and activate the plugin for it to start recording all the important data to the database. It basically detects all the visitors who arrive to your blog from the Search Engines and uses the information to link to those respective posts. While the plugin won’t link to all the keywords it would make a note that if the ranking for that specific keyword or key-phrase in on the second page of the Search Engine, then it works, and if the posts ranking moves towards the first page, then it wont record that specific keyword.
Basically it wont link to the posts when the rankings get boosted reducing the load on the database too. Here are a few screenshots of the reports this plugin is going to give you in the Admin Panel and how this information can be helpful to you for making the Long Tail Key Phrases rank better.
Top 10 Search Queries (includes Page 1 results, excludes archived records)
Links that will be shown in widget