Know your surroundings. Take a few moments when you arrive to acquaint yourself with your surroundings. If you can arrive early, go to the podium and do a soundcheck before your audience arrives. If you have visual aids, practice using them while you are orientating yourself with your surroundings.
Take the time to really know the material in your speech. Don't just memorize words, understand facts and even have a relevant story or joke on hand. Work them in where you think they fit and will engage your current audience. Also, use them to answer questions and back up the substance of your speech.
After you have committed the speech to memory, make sure you keep practicing. This will allow you time to tweak the speech if needed. Learn to breath with ease and pace your delivery. Ensure your speech allows for interruptions, such as applause. When you can, try out your speech using the exact equipment used in the public event.