Be sure he understands your competitive advantage, and the actions being taken by others. Customize this to link closely with current business issues. Be sure the person who introduces your speaker is well prepared and enthusiastic. Help people remember and apply key points with an attractive take-home handout. Be sure your speaker has access to the room prior to his presentation.
Professional speakers have vast experience with room layouts, acoustics, lighting, etc.
Try to make the changes your speaker may suggest. Small improvements can sometimes make a very big difference. You may allow a few minutes for discussion amongst audience members before taking the first question. Provide microphones for your audience to ask questions. Your speaker should clearly repeat each question for everyone to hear.