I don't know where to click, what link to follow, where to order.
One of the crucial elements of an email marketing campaign is a clear call to action.
- Lay out exactly what you want the recipients of your message to do, and
- design the message to make that path clear for the recipient, and easy to follow.
Don't distract with too many links or offers, and make not only the call to action clear but also what recipients can expect when they click through. This can be as simple as "Click here for a 20% discount on your next weekend trip."

