The document outlines 10 common mistakes made when building email lists: 1) Making assumptions without testing, 2) Only testing small changes, 3) Using double opt-in which slows growth, 4) Not having a strong offer to entice signups, 5) Not delivering on the offer, 6) Having an autoresponder that doesn't send emails quickly, 7) Only providing one way to subscribe, 8) Relying on a single traffic source, 9) Using a stock squeeze page without customization or testing, and 10) Buying subscribers which results in unresponsive contacts. The document encourages testing to optimize the list building process.