Any metric you're tracking should be one that informs how your business moves forward in a tangible way. Your overall number of followers can give you an overall idea of how you're doing but it doesn't tell you how to move forward.
According to Jay Baer's presentation A Field Guide to the 4 Types of Content Marketing(http://www.slideshare.net/jaybaer/a-...marketers_tell) there are four types of metrics you can track to inform your business decisions:
1) Consumption Metrics
How many people listened to/watched/read/downloaded your content? This is fairly easy to evaluate for each individual post on all social media networks.
2) Sharing Metrics
How many people have shared your content? How much does this piece of content resonate with people? Social media networks automatically show this kind of information, but if this is your focus for business you'll want to use one of the tools listed below.
3) Lead Generation Metrics
How often does consumption of this content generate leads for your business?
4) Sales Metrics
Did this content earn any money for your business?
The important thing about all of these business metrics is that you can use them not only to assess whether or not a campaign was a success but also to shape your next campaign. All you have to do is choose to track the metrics that line up with your goals for the campaign--and you might end up tracking a different metric for every advertising campaign. This is fine and even to be expected. The metrics that matter most to you will depend on your business model, which is bound to change over time.
Another way to track your social media metrics all in one convenient place is by using a specialty program like TrueSocial(https://www.truesocialmetrics.com/). It does cost money but it makes tracking any metrics you're interested in simple across all of your social media accounts.
What social media metrics are you tracking? How do you track them? Have you ever considered using a program like TrueSocial? I'd love to hear about it!