Use titles to reinforce your main point. Your titles should be meaningful, specific and brief while the supporting points have a take away point. According to Lisa B. Marshall, a public speaker and author, you can assert your message more by making your point then providing evidence and then making a point again (PEP). Match your communication style with your audience's level of understanding.
Concentrate on the message you want to deliver by using action verbs to avoid vagueness. Ensure your announcement appeals to your audience's logic, emotions and character. For instance, if you are appealing for help, use graphics and words that your audience will identify with and persuade them to relate with the need. Use quotations to make your point where appropriate and ensure you include your contacts at the end of the announcement. Tell your audience what you want them to do after hearing the announcement.
Use well-designed slides specifically done for the announcement; each slide should contain the message you intend to deliver. Ensure the background of the slides, color and fonts chosen complement each other to maximize their effect. Make all your slides flashy by using only appropriate graphics and visual illustrations. Ensure your slides have proper use of white space.
Allocate adequate time for each slide so that you don't rush your announcement or risk interruption; the time allocated would be approximately one minute. Make your announcement catchy by keeping it short and leave each slide up while you explain them to allow the audience to absorb the message.