First consider the people attending your meeting. It's not enough to plan from your perspective alone, since each of us "sees" differently. Plus, if your intent is to deliver a message or solve problems, you need to adopt a relational approach. You're not just talking to folks; you're relating with them. You're trying to understand where they are coming from so that you can link with their ideas and feelings, at least enough to get your point across if not persuade them to your way of thinking.
In planning, you need to think from the other side of your desk and deliver your talk or conduct your meeting with listeners' viewpoints in mind. Here is information you should know about your audience before you convene a meeting.
Gender and age. You might not do anything differently if the audience was largely male or female, but your supporting material could be slanted toward either. Age could make a difference though; talking with retirees or elementary age children would require different focuses. If the crowd is mixed, try to tailor a few remarks to each.
Education, job/profession. High school graduates and Masters level people would hear you quite differently, as would nurses and retail workers, to name a few. Again, if these are attending a PTA meeting which you are planning to address, be aware of the level of language you use and aim for the middle ground.
Setting. Small groups behave differently from large ones. Sitting at a table on a dais calls for adjustments as much as having a meeting "in the round" with people surrounding you. Checking for AV equipment ahead of time is a good idea. Addressing "suits" is different from addressing a college crowd.
Expectations. Does the crowd want entertainment or some serious thoughts? Is this more or less a social gathering, or will the group break into smaller groups and discuss what you said? Are you team-building (rah!) or are you telling folks the plant is closing?
Now comes the hard part! You have to ask yourself what this group would consider important—and plan your meeting from that direction. Empathizing with your audience, walking around in their moccasins for a while, will help you get into their mindsets. What questions are they likely to ask? Get answers in advance; include them in your talk if you prefer. How can you make your message memorable? Even if you're planning meetings for a small work group you know, think about the issues you're bringing up and how they are likely to respond. Open your meeting by asking them what they want to know, and then provide the answers you've prepared. Listen attentively to their problem-solving suggestions, and treat them with respect and courtesy in decision making. Buy a new outfit for the "Great Boss" award ceremony.