Index Most Effective Ways in Writing Professional Email Subject Lines. #1: Start with Action-Oriented Verbs. #2: Make Subscribers Feel 'Exclusive' #3: Create a Sense of Urgency & Scarcity. #4: Ask a Question that Begs to be Answered. #5: Invoke a Level of Curiosity. #6: Get Controversial. #7: Leverage the Power of Free. Jun 15, 2022