The document discusses 4 ways to segment users for marketing purposes: 1. Use pre-defined segments that are standard for a particular industry or target common use cases. 2. Create rule-based segments based on specific marketing goals and analytics to target niche audiences. 3. Use machine learning to identify segments that are most likely to engage and convert based on customer data to predict potential buyers. 4. Evaluate marketing hypotheses by running campaigns on specific user segments through discovery to test any hypothesis and use historical data to create new segments.