Also, you'll want to familiarize yourself with the layout and introduce yourself to anyone who will be in charge of lighting, audiovisual, etc. Another advantage of arriving early is that you then have the chance to meet and greet all or some of the attendees as they arrive. It is directly related to whether they will want to engage your services. Whatever you do, don't bore your audience will endless detail. You are likely to make the seminar more enjoyable by making it interactive.
Some presenters invite the audience to ask questions as they occur.
Once potential clients feel that you're technically competent, they then focus on whether they LIKE you. In giving your seminar, make sure you provide top-notch information, but also make sure that you do it in a way that makes you approachable and likeable. While your seminar has the purpose of imparting important information to attendees, you should also make sure that attendees walk away with a real understanding of what their unmet legal needs are. Ideally, they should also have a grasp of what the consequences are if they fail to address those needs. For example, if you're talking about estate planning, many attendees may not be aware of the repercussions of dying intestate or of the messy complications that can arise for survivors when proper estate planning is not done.