A great headline creates a "curiosity gap" — it provides enough information to interest the reader but leaves them needing to click to get the full answer. Combining this with a clear benefit is key.
It depends on the platform. For Google Search, keep it under 60 characters to avoid truncation. For YouTube, the first 45-50 characters are most important. For social media, shorter is often better but clarity beats brevity.
Avoid "bad" clickbait that misleads. Use "good" clickbait — intriguing headlines that actually deliver on their promise in the content. If you trick a user, they won't come back.