Whilst it's interesting to know how many followers/likers/contacts you have it's not the best way of measuring how effective you are and what impact you're having. If you have 40,000 followers on Twitter the chances are you're all following each other because you all automatically follow back. There's no engagement, no reputation gain and even fewer sales.
My advice is to keep it simple!
Try adding some of these to your metric mix and see what story they tell you about what you do.
This is available from your admin panel on your business page. It allows you to see the number of people that have had the opportunity to see each post you make. I find it really useful as it enables me to hone the content of a page so that it's interesting - and therefore gets more likes and shares.
How many people have talked to you or about you? Personally I don't count automated content, such as the daily paper tweets, as they require no real time input from a human being.
Posts (Facebook, Twitter and LinkedIn)
How often have you posted each week?
If you've altered your post frequency, how has it affected your statistics?
What do you need to do now?
Clickthroughs (Facebook, Twitter and LinkedIn)
What was the clickthrough on any links you posted?
Where did you get most success? Even if the link wasn't to your site or blog, the content of the highest clicked links can inform you of the type of content your community want to read.
Referrals (Facebook, Twitter and LinkedIn)
How many people recommended you this month? I don't mean in a bulk #followfriday on Twitter or a courtesy name check after networking. I'm not knocking these, but they are in the category of mentions rather than referrals.
Blog comments and followers
This is one area where the built in statistics package really is your friend. Blog hits are a good way of seeing how much you're being read, and where those readers found you. Monitor your content, see what sparks interest and write some more, or at least use the same style. Comments are, mostly, good news. Just make sure your spam comment filter is set up correctly.
There are so many different ways of measuring social media, these are just a few of my preferred metrics. I haven't even touched on evaluation by algorithm such as Klout or Kred. I don't use any of the sites that purport to measure "reach" and "influence" as I disagree with the way the algorithms are set up. Perhaps I should write my own...