Although there's no substitute for knowing your subject matter, being well organized can help you survive the critical eye. Lead the viewer step by step through your research by dividing the poster into discrete elements. Traditional wisdom holds that, at a minimum, you should include title, abstract, introduction, methodology, results, and conclusions. Depending on the stage of your research, however, you may also want to include sections on future research plans, questions for discussion, etc. Be sure to leave white space between sections, so that each stands alone.
Text size is also very critical.
It must be large enough to be read at a distance, because if you attract a crowd, it may be difficult to get close to your poster. Generally this means a font size greater than 100 points of your title, and greater than 18 points for the body of your poster's text. There are several approaches to assembling your final poster. Perhaps the most common is to wait until the meeting, and then pin your text and graphics blocks to the bulletin board provided for you. For a more polished look, you may want to assemble the poster at home on pre-cut matte board, available from most art supply stores and framing galleries.