When planning an important meeting (such as a medical symposium or healthcare customer meeting), it is important to produce invitation material (flyers, postcards and emails) that instantly capture attention.
Capturing attention is a per-requisite to compelling more people (or the right people) to register.
Referring to some basic principles of adult education and instructional design can be very helpful. As a starting point, here are a few helpful questions/suggestions:
Which element of the meeting is the big draw?
Is the speaker world-renowned? If yes, then a picture will speak a thousand words. Include a good quality head shot and feature it prominently on the flyer. Include the speaker's name in bold and credentials/affiliations in slightly smaller font.
Does your flyer have lots of white space/uncrowded layout?
Text-heavy flyers are so yesterday. Use Twitter as your inspiration and limit your words and characters. Add clickable hyperlinks and a call to action
Use large, easily readable font (no italics) for essential information.
Essential info includes name of speaker, date and time. The location is slightly secondary so that information can be slightly smaller font.
Does the meeting sponsor have a tangible business interest in this meeting (i.e. more than just good will)?
If you answered yes, then the company their logo should not be as prominent as other elements ont he flyer. A small version of their logo can appear in the bottom right corner.