I take the approach of getting both quantitative and qualitative measures, both bottom line (e.g. revenue) and project-specific (e.g. collateral usage) metrics.
Quantitative metrics include: revenue, win/loss rates, launch metrics, product usage, retention
Qualitative metrics include: internal feedback (e.g. sales team surveys), external feedback (e.g. brand awareness surveys)
A little bit more on that here, with suggestions from other product marketers: https://www.crayon.co/blog/product-marketing-metrics
Full disclosure, I work for Crayon, a market & competitive intelligence company. Here are some initial thoughts based on my experience building a CI program here and at previous companies, as well as what I've learned from our customers.
Agreed with the other answers about aligning impact with focus areas for the business as a whole. Though I also like to have some consistent metrics to be able to see some longer term trends.
There's a separate thread here that dives into PMM metrics:
Some good points there about the combination of quantitative and qualitative metrics, and even quantifying some of that qualitative feedback.
1. Automate as much of the research / data collection as possible. (I'm biased, but I think Crayon does the best job of capturing competitive moves across millions of sources.) Honestly, this should be "outsourced" to technology because it can do a better job at a fraction of the cost (think of your time) and time (enabling real-time analysis and action).
2. Prioritize what you find. Not everything will be critical, so take a tiered approach - by groups of competitors (tier 1, tier 2, indirect competitors, emerging competitors) and by type of update (acquisition vs. new ebook). This will keep you sane and make the CI more digestible to the various internal stakeholders consuming it.
3. Set goals and get agreement beforehand. Figure out what you want to capture, what you want to impact internally, which competitors you care about most, etc. Get agreement internally so that everyone who cares about competitors are on the same page.
I prefer to have a two-person team to do interviews - one person to conduct the interview, the other to take in-depth notes and identify follow up questions. This can be less critical if it's possible to record the interview, but I find that the written notes are fantastic for sharing the takeaways with others afterwards.
I found this post pretty thorough in terms of a process, questions, etc: https://labs.openviewpartners.com/how-to-conduct-win-loss-analysis/#.W2OIs9hKjVq
I referenced it when writing about a broader win / loss analysis process: https://www.crayon.co/blog/how-to-do-win-loss-analysis-examples-resources
Oftentimes, "win / loss analysis" gets equated with prospect interviews but it's just as important to measure the overall trends - both for tracking changes over time but also for identifying areas you want to dig into during the interview process. For example, you may see that a common loss reason is "budget", so you can dive into budget questions in your interviews with both won and lost opportunities.