Engagement is not how many "likes" your company has on Facebook. It is a continuum, ranging from click-throughs on the low end to advocacy on the high end, measurement guru K.D. Paine told members of PRSA and Mile High Social Media Club in Colorado.
Return on Investment may be efficiency, not sales: finding the relevant people to engage with and building long-term relationships.
Another mistake is to select a measurement tool (such as media monitoring) before deciding on the goal. As examples, a metric for reputation/relationships could be a percentage increase in recommendations, while a sales goal might be an increase in qualified leads.
Six Steps to Measurement Success
1. Define the "R" in Return on Investment (ROI)
2. Connect the dots between organizational goals and PR programs
3. Establish benchmarks to reach the goal
4. Define the metrics to measure progress
5. Pick a measurement tool
6. Figure out what it means, make changes and measure again.