1. Limit your text. A good rule of thumb is 1/3 text to 2/3 visuals.
2. Images should be able to capture attention and relate to the purpose of the poster. Don't overload your poster with too many images.
3. No more than two font types and only three or four font sizes. Remember the size reflects the order of importance the size of the text.
4. Don't go overboard on color. The background should be a muted color or should contrast the text color. Avoid black background for printing purposes. (It eats our ink up)
5. When it comes to layout, leave lots of space. Control the eye flow by grouping information logically and using space to draw the reader through the layout.
6. Design more than one layout. Try different colors, fonts, sizes, arrangements, ideas... A designer rarely comes to a client with one choice. Show your versatility!
Don't forget that posters are for reaching a large amount of people in certain areas. What can your design do to intrigue the viewer to check it out. What do you have on your poster that allows the viewers eye to move through the information. Usually start with the most important information at the top and follow in order of importance. Display the information in such a way that the eye follows this information. Be original. Try for something different than what's been done before. Don't let an Adobe Illustrator document look like it was a Miscosoft Word document. Create something that shows your own talent and pride in your abilities.