Write down the stages your last few customers actually went through, give each stage an exit rule, and track every deal against them. For most B2B businesses that is lead, qualified, discovery call, demo or proposal, negotiation, then won or lost, and the exit rule says what must be true to move on (a booked call, a named budget holder, a sent quote). Put the stages in a free CRM pipeline such as HubSpot's, log every deal, and after a month count how many move from each stage to the next; the stage with the biggest drop is where you work first. Run real discovery before any demo, and once deals get larger, qualify with a checklist such as MEDDPICC. To know whether you have enough in the funnel, divide qualified pipeline by your target: $1.5M against a $500K quota is 3x coverage, read against your own win rate. The rule: a funnel is a record of how customers buy, not a diagram of how you wish they did.
The reference explanation of all eight letters from the people who own the methodology, free to read. Use it as a deal checklist: the letters you cannot fill in are exactly where your deal will die.
Explains why the 3x rule of thumb is wrong for most teams and shows how to derive your own coverage number from your actual win rate. Weighted versus unweighted coverage is handled properly too.
The whole 400 page book is readable free chapter by chapter, written specifically for founders and first-time sellers rather than career sales people. Chapters 4 to 8 (prospecting, outreach, pitching, closing) are the ones to read first.
It orders the seven ways early customers actually arrive (network, cold outbound, investors, community, content, press, launch) by how much trust each one starts with, which is the missing map for a first-time seller. Built from interviews with founders at Figma, Notion, Databricks and Slack rather than theory.