This document provides tips for writing effective email subject lines. The key points are: 1) 80% of people only read the subject line, so spend 50% of the email writing time on it; 2) "About me" subject lines focusing on the reader work best; 3) Subject lines should be clear and avoid being misleading or cryptic. Testing different subject lines is important to see what works best for a particular audience. The document provides additional guidance on formatting, words to use or avoid, and learning from successful marketers.