Creating a clear subject line involves several key steps: 1. Be Specific: Clearly state what the email is about. For example, "50% Off All Winter Coats" is more effective than "Big Sale". 2. Keep it Short: Aim for 6-10 words. Shorter subject lines are easier to read, especially on mobile devices. 3. Use Actionable Language: Encourage action with verbs. For instance, "Download Your Free Ebook Today" is more engaging than "Free Ebook Available". 4. Avoid Spam Triggers: Words like "Free", "Urgent", or excessive punctuation can send your email to the spam folder.