Match the source
When possible, reflect the wording and intent of the ad, email or search result that sent the visitor.
Name the outcome
Lead with the result or useful change rather than internal product language the visitor may not recognize.
Add specificity carefully
Specificity increases clarity when it is true. Avoid invented numbers, guarantees or timeframes.
Use the subhead for context
Let the headline carry the promise and the subhead explain audience, mechanism or important qualification.