Do a dry run for your group and get some feedback. Check your presentation for length and content. If it bores members it will bore non-members. You will want to have your most important messages in the first five minutes of your presentation and ideally the whole thing should be no more than fifteen minutes long. Long complex and rambling presentations are not good tools to recruit members unless you are trying to screen out everyone that gets bored easily.
Slide shows are a great tool for giving lots of information to many people in a short time.
People will evaluate your community by the presentors. Choose presentors who are good ambassadors for your group. Try to have a variety of types of people from your group. People make judgments about how much like them you are. If you have a variety, you will match more people.