The number one tip is to split test messaging by serving two invitations for the same rule. Not all rule engines allow this but for the ones that do, this is a powerful feature. A popular best practice is to send specialized invitations to visitors who arrive on-site through pay-per-click ads shown for competitor keywords. Another tip is to include special offer messages in your invitations. Finally, our research shows that invitations which allow visitors to type in a question directly (via a built-in form) are nearly 50% more likely to be accepted. This seems to indicate that one possible persuasive technique would be interrogatory statements.