Your message should be as bold and clear as possible with blocks of text and images to support it. Use your title as a tagline to sell your poster to the audience and make sure it is focused throughout. Use strong statements supported by data and don't forget to re- affirm your main points in the conclusion.
The purpose of your poster will vary depending on the context and nature of the work being presented, as well as its main intention. Whether your poster is submitted as an assignment or for a conference, ask yourself what you want the person looking at or passing by your poster to do, as a result :
Shape the message of your poster according to how you answer.
Image by Conrad Bakker available CC BY-NC-SA on Flickr