Are you using Google Analytics to track your traffic stats?
If so, do you have goals set up for your website including tracking optins, sales, leads, etc.?
I'm often shocked by how few clients are TRACKING the results of their visitors. This is probably one of the easiest ways available to see the ROI of your websites, Facebook posts, Twitter usage, and everything else you're doing to bring visitors to your site.
This video shows you the basics of getting your first goals set-up.