This document provides 10 secrets for quickly validating a product idea with real customers before building it out fully. The secrets include: 1) Writing down the product concept and assumptions; 2) Deciding to test assumptions like a scientist; 3) Finding people with the problem; 4) Starting validation with your own network; 5) Interviewing people and asking open-ended questions; 6) Finding the value proposition; 7) Recognizing that liking an idea differs from buying; 8) Challenging customers politely; 9) Having fun validating before fully building the product. The overall message is that validation is easier than full product development.