Ideally, you would use the services of both a designer and a copywriter to create a great flier. The former would make it visually attractive and the latter would make the text right for your purposes. Such services easily pay for themselves, as the same flier can be used over and over again for all kinds of events.
If you produce a flier on your own, there are a few basic rules that you should follow. First, from one fourth to one half the flier should be taken up by the key word or phrase (e.g. OUT-OF-BODY TRAVEL, LUCID DREAMING, ASTRAL PROJECTION, etc.). This will allow even the somewhat nearsighted to read it from afar. Otherwise, people will all just walk past it – nobody wants to go up to a flier and read small print without first knowing what it’s about. Second, one shouldn’t try to fit too much information on a flier. Stick only to what’s most important: what, where, when, and contact information. The description itself should consist of no more than a few highly-motivational sentences. Third, you should briefly point to how people can use the phenomenon in real life. The applications that get the best response are obtaining information and self-healing. Fourth, design the flier so that the background makes the text stand out, instead of camouflaging it.