WOMMA have just released a Measurement and Metrics Best Practises Guidebook to help the industry how to track and measure the impact their campaigns have. Here is my summary of Ed Keller's summary. Click on his smile to go to the article.
Conversation volume and share: the overall amount of word of mouth about a product, service, or brand (or topic such as the environment or health/nutrition). It is the word of mouth equivalent of sales volume, or consumption, or audience size. Measurement of conversation share looks at a group of brands and the amount of conversation each enjoys versus the total for all the brands combined. It is the equivalent of market share analysis.
Reach: Whereas conversation volume represents the numbers of messages or outputs via word of mouth or social media, reach measures the number of people who have been exposed to word of mouth content, either directly (via the sender of the word of mouth message) or indirectly (via the retransmission of a message to a second or third generation of recipients).
Sentiment analysis: An analysis of a speaker’s tone when talking (or posting) about a brand or product (e.g., positive or negative), and the intensity of opinion.
Content: Monitoring what exactly is being said about a brand during online or offline conversation. Verbatim comments can be read as qualitative insight into conversations in which we look for things like passion words (love/hate, fantastic/awful, etc.); or unexpected uses for products of a product or shortcomings you weren’t focused on; or the "everyday" language that consumers use when talking about your brand to help with marketing messages or keywords.
Advocacy: Advocacy measurement identifies all of the different ways people verbalize their advocacy, isolating advocacy terms and emotions from general positive sentiment (e.g., I might like five different car brands but will only tell my family and friends to buy one of them). It also explores who is doing the advocating to help profile the dynamics of brand advocates.
Actions taken: To help determine the extent to which positive word of mouth or brand advocacy links to behavior. The behaviors measured should be tied to your marketing goal. Are you trying to drive sales, or visits to a website, or sharing of a coupon, or forwarding of a link.
ROI: If ROI is important to you, it’s important to determine in advance of your marketing initiative what the formula for evaluation will be and to build the metrics for measurement in advance of launching

