Know your user cohorts
One of the most important tools to better understand the usage of a web application – or a service, a game or a mobile app, it doesn't matter – is a cohort analysis. In fact, it's almost impossible to get a really good understanding of a service's usage without looking at activity and retention numbers on a cohort-by-cohort basis. And yet, most startups that we're talking to haven't looked into cohort analyses yet. Often the reason is lack of resources. If you're a young, bootstrapped startup and you have to decide if you want to use your developers' scarce time to improve your product or to get better statistics most founders will decide for the product. That's understandable. Nonetheless I would like to argue for a high quality standard of metrics early on, since the insights that you'll get by understanding your metrics will often be highly actionable. And of course it will make your conversations with investors who want to understand your numbers...