I hadn't done this for a while, although it's something I should do regularly - but with the shake up in the serps post panda I just did this and found a few surprise rankings, so thought I'd share it as a reminder. Firstly you'll need to have GWT - so all you conspiracy theorists out there move on. You will also need a pretty good piece of ranktracking software - i use ranktracker as it's up to the job. Finally you'll need some patience if you've got a biggish site. This task took me 76 hours for a 600+ page site. Open GWT and click on search queries - then download the whole list. This is a list of all the searches your site features in - not what you target. This will be a pretty big list so you may want to open it in excel and maybe trim the obvious crap to make the next step a little quicker - I don't bother. I do however clean the list of my usually checked keywords, as I know about these already. I then set ranktracker to check only the first 20 or 30 results. Remember you're trying to find things that rank page #1, or that could be easily bumped to page #1, not simply how many terms you rank top 1000 for. You could set it for more but it'll take forever and you'll possibly ban your proxies sooner. I ran this over the last few days on a list of about 6,000 terms on G and G.com.au, and found some real gems ranking top 5 post penguin - stuff I had no idea I was ranking for, with pages I had no idea were ranking. Now to simply optimise those pages a bit and give a bit of a push to some great potentials sitting #6 to #20.