Meetings are about transmitting a message to the audience. If your audience can't hear the message, what good are we doing ? As a meeting planner, how many events have you been to where you couldn't hear the speeches ?
Rather than going into a technical explanation of what makes good sound and how to get there, I think that if you take a few ideas along with you when you talk to your sound vendor, you can help to improve the sound at your meetings and events.
When planning a sound system for a meeting or event, here are some of the factors I would take into consideration;
The size of the audience - People absorb sound. The more people in a confined space, the louder the sound system will need to be to compete with not only the absorption from the audience, but also the general crowd noise.
The physical space - Acoustically speaking, there is a large difference between providing sound in an all glass atrium and a outdoor amphitheater. Although those are extremes, knowing the size of the room, including the ceiling height, is a good start. It would also be helpful to know about wall and floor coverings
The ambient sound levels - Once again, I would supply two very different sound systems to a meeting in an office, as I would to a meeting on an airport runway. What is the background sound levels that the sound system will need to compete with ?
The type of event - Knowing the expectations of the audience as well as the client plays a major factor. Is this a conference where the intelligibility is the goal, or is this a concert where the goal is to create the appropriate environment. Loud and powerful for concerts and dancing, or subtle and evenly dispersed for cocktail parties or trade shows.
The best idea, of course, is a site survey. Taking the extra time to walk the venue with your audio vendor will benefit you immensely. It is also a good opportunity to express any concerns you have about the event. At the very least you should take the time to speak with your audio vendor and making sure all these factors are relayed.