The best thing to do is analyze what keywords you are ranking for. An easy way to do this is Google WMT and looking under the "Queries" section. Can't remember if it tells you AVG pos. or not. I've been using SEO tools and trackers for so long, I only check WMT if necessary.
Look for the keywords that are getting minimal impressions.
Then find the pages that those keywords might be located on. Most of the time this is pretty easy.
I use SEMrush and it's $149 a month but it's not just a keyword rank tracker. It tracks my comp, their backlinks, etc.. and so much more I need it for.
So I would just plug my site into SEMrush and run an audit and tracking on the site. This would tell me what keywords I am ranking for. Obviously focus on the easy ones first. Position 4-20 in Google. Any keywords ranking there would be my first target. I would re-optimize the page for the KW getting the most traffic and use others as LSI.
Then I would share the site to all of my social networks. Outsource social shares, likes, comments, social bookmarks, and possibly get a press release done and a couple web 2.0 links and PBNs. Bam! 1st page yo! Everytime. I coach bloggers on this type of shtuff. Big market out there and usually they're ranking on the second page for multiple KWs and don't even know it!