Measuring Engaged Customer Advocates: Strategies and Metrics

I'm sure this has been discussed before, but I must ask again 🙂 How are you all measuring engaged customer advocates? For example, say we want to increase the # of engaged customer advocates QoQ, how do we start measuring this? We're thinking of an engaged advocate as someone who completes an act of advocacy... that can be broad so would love to hear if others are thinking this way.