Generate an analytics report you've never used before, or spend 20 minutes looking at reports you don't check often. Use Google Webmaster Tools to check for duplicate titles, descriptions, content... Completely new keyword research report (if not done in past 6 months) Find keywords you rank in top five for on both the first and second page of Google. Try to bump up the page 2 listing to skip some spots and get the indent.
Check and compare PWS=0 VS standard logged-out Google search for your top five keywords. Is there room to capitalize on video, blog, shopping or other universal content? Try a new tactic (for insta usa email database nce or for instance) that you haven't tried yet. Spend 20 minutes browsing your top competitor's website looking at everything SEO-related, including content. Create one variation (singular, plural, possessive, synonym...) of your five top-performing keywords and write and publish content for those keywords.
Check first three SERPs on each engine for negative stuff. If nothing is there, search for things like "YourCompanyName Sucks" or "YourBrand bad customer service". Subscribe to brand mentions on Twitter and elsewhere. Check log files for suspicious activity or anything else that stands out. Check internal site-search logs for queries that returned zero results. Those are opportunities your readers/shoppers are telling you about. Check referrers. Look for anything new, unexpected or suspicious.