From Business Goals To Events

Good measurement starts from decisions, not from data. Work down a simple chain: a business goal leads to the questions you need to answer, which imply the metrics you need, which tell you the events to collect.

For example, the goal "grow trial signups" raises the question "which channels drive signups?", which needs the metric "signups by source", which comes from a sign_up event carrying the method. If an event does not help answer a real question, you probably do not need it yet.