Professional conferences often have a category of presentation called 'poster sessions'. Poster presenters hang their posters on panels for passers-by to see; the role of the presenter is to discuss the content with interested people. Poster presenters are generally given a public area for their displays, in close proximity to one another, and designated an amount of time, whether it is for a day or only an hour or two.
If you have ever seen poster presentations, they may have contributed to your fond memories of past conferences. To people who have experienced successful conference poster sessions, or presented one themselves, the points I am about to make may be readily apparent.

Why do people appreciate posters?

Well managed, designed, and presented poster sessions are a hit with conference goers for a number of reasons:

They provide a greater diversity of easily accessible and 'fresher' topics.
They provide a greater opportunity to interact with presenters on personal terms. This includes influencing the time commitment to the topics - you do not have to sit still for a full hour - control over the flow of information through questions and turn-taking.
They provide an opportunity to find more discussants and potential collaborators interested in similar topics. This is not restricted to presenters; other people in the audience enrich the presentation discourse.
They provide an opportunity to survey a larger field of topics in a shorter amount of time. Teachers are often generalists, needing to know about and having interest in many topics. A siz-able poster program should usually have enough of interest to suit teachers in close proximity.
They are something you may be able to experi-ence enjoying a cup of coffee and nibbling on a snack. Stretch your legs and give your bum a rest.

Hopefully, these points will become more apparent as we examine the question of 'Why?' from the presenters' perspective.

Why present a poster?

Given a choice, why should a presenter choose to give a poster presentation rather than a lecture type?

One obvious answer is that a choice is not always presented. Deadlines do not always present themselves at convenient times for composing thorough and clear presentation proposals, and the criteria are often less critical, and the deadlines later, for posters. Also not everything that is of professional interest and valuable to a wide swath of teachers fits neatly into the rubric of 'academic' or 'research', nor extensive enough to merit the allotment of valuable program resources. Topics, selection procedures, or personal circumstances may dictate that a poster is the singular way to go.

Another answer is that a popular poster session venue may provide much greater exposure than available alternatives. My poster presenter correspondents have reported passing out more than 200 handouts within a two-hour session. Unless you are a keynote or plenary speaker you can hardly expect to do better than that. But this comment about greater exposure does not refer to quantity alone. The same correspondents and conference goers report that they experienced much more personal interaction with others through poster sessions. On the one hand this meant presenters could respond directly to questions their audience wanted to pose, and on the other they could treat their audience as informants. Their audiences were able to talk about their own experiences with the topics, provide perspectives on future directions for research, and indicate important gaps in studies in the most constructive ways.

Some people also prefer the casualness of presenting a poster. This is partly a result of the non-linear quality of posters. Rather than introduction, body, and conclusion with question time (if any) reserved for the end, posters are more like progression through the Internet, with visuals suggesting links for discussion. After all, with people coming and going at irregular intervals it hardly makes sense to develop a long monologue; the audience at the beginning and the end will have changed. For new presenters, especially, this approach is less daunting and has the advantage of informing possible standard presentations at a later date.

This does not mean posters are easy. A poster requires people to present simply and clearly; which is actually very difficult. Poster presenters must invest a lot of time distilling their topics into a few very accessible - but often very profound - topics. They must consider how to use graphic design concepts to accentuate and define ideas and hierarchies. In effect, the audience must be able to understand some fundamentals of your presen-tation at a distant glance. It is hard work. The advantage for the presenter is the dynamic impact and potential to inspire others that a successful poster presentation can have.

Why include posters in the program?

What should be emphasized is the potential for poster sessions to contribute diversity to the standard program. Posters provide an alternative for conference attendees who have tired of sitting quietly for long periods in regular sessions. They provide opportunity for conference goers to peruse various professional topics and perspectives in between a bite to eat, planning their day from the conference schedule, and attending the next plenary session. Furthermore, the content of poster sessions can be very diverse and offer many contrasts to the standard sessions. Poster sessions often have a 'fresher' appeal to them as a result of their being on-going, or just completed, projects. In this last respect, poster sessions offer prime opportunities for interested conference goers to meet and collaborate on on-going research.

The point to be made here is this: poster sessions can contribute uniquely to a conference and the quality of its program. To be successful they should be given a central, high-traffic, location and a pop-ular time block. A time should be arranged during which the audience can be certain of meeting the presenters and discussing the posters. This will make people enthusiastic about poster sessions and eager to see more in successive years1.

Suggestions for further action
Poster presenters do not have much in the way of precedence to either guide or restrict them. This presents both challenges and creative opportu-nities. However, here is some general guidance:

Keep in mind the four design principles.

Alignment simply means consistency with using 'edges' of text, graphics, and posterboard. This not only makes displays more attractive, it makes ideas fit together better. Try to use axes symbolically and methodically; for instance, main ideas on a vertical axis offset by examples opposite on the horizontal.
Repetition of features, like alignment, helps to integrate the design parts of your presentation. Holding the parts together in this way creates an organized impression. Repeating colors, shapes, font shapes and sizes, and placement create repetition.
Contrast creates the dynamic tension, opposed to repetition and alignment. Whereas repetition and alignment create harmonious integration, con-trast injects drama and calls out for attention. Bullets in this article contrast with the other paragraphs, as do bold font, indentations, and italics. Without any visual impacts this paper might seem rather dull. If everything were bul-leted, bold, indented and italic the effect would be extremely messy. In general, use contrast spar-ingly but boldly and meaningfully. Starkly varying the elements of repetition creates contrast.
Spacing is something which creates both uniformity and contrast, so it is especially important to order in graphic design. Generally, group or cluster closely related information and somewhat isolate them from other elements with white space. White space is our friend; resist the urge to crowd in ever more detail. See how white space is used in a well-laid-out book to divide sections and chapters.

Think ahead.

Give yourself plenty of time ... and space ... to design your display. Know how much space you have to work with.
Do not trust memory alone. After you have laid out your display, number the backs, take a photograph, or somehow record your final deci-sion. It is easy to forget in the minimal amount of time available for pinning up your display.
Design the display with transportation in mind. If you are going to carry the display to the conference as large sheets of paper folded in your suitcase, design it so that the folds actually accentuate, or at least do not detract from, the visual impact. Assemble as much as you can before packing.

Your handout.

A handout is a very useful element of the presentation. On the one hand it can complement the display, providing extra detail which minimizes the need to crowd the poster design, and on the other participants will use it to recall you and your presentation. In this latter function it is extremely helpful if the handout mirrors the poster. The handout's length in number of pages can be minimized by creating an online extension. The URL should be cited on the handout.

A unique format

In the end, poster presentations are a unique format with their own strengths and weaknesses. One important advantage is that the format is accessible to a large number of participants because it does not require many resources. Part of the underlying philosophy is that we have as much to learn from our peers as we do from the profession's leading lights. Posters should be an attractive way to present, and an attractive way to enjoy a conference, and hence an economical and attractive way to expand conference programs.