When you invite others to your presentation, send a thoughtfully written agenda with a concise but revealing subject line—and be explicit about what the audience will get out of it. All communication leading up to your talk will affect your credibility and impact—so put as much thought and care into it as the presentation itself. It might be useful to send a slidedoc as a pre-read.
Special touches in the room let people know what to expect and prime them for the type of experience you want them to have. If you’re giving a calculated, chilling speech, maybe a cold, sparsely appointed room works. Use bright lighting for a casual talk; go a bit darker for a formal one. Provide refreshments (even for small, familiar groups) to make people feel welcome. Music, props, and projected images can also help set the tone.