This document discusses the freemium business model and provides advice for companies considering it. Freemium relies on the irrational behavior created by offering products or services for free. It works best for solutions targeting large markets where marginal costs are low and the product is highly engaging. The document outlines best practices for streamlining signups, driving conversion, marketing effectively, controlling costs and metrics. It analyzes case studies of companies that succeeded or struggled with freemium implementations. Overall, it argues freemium can be effective when properly executed for the right type of product or service.