Measuring your success with social media is key. It's one of the reasons I have a job. I really understand the importance of measuring what works and doesn't work, looking at our click-through rates from Facebook, Twitter and LinkedIn, and how much traffic this drives to our website.
Along with Google Analytics, I utilize the statistical feature in Hootsuite. I think Hootsuite is a must for any social media manager or anyone who is consistently managing a social media campaign on different platforms.