-Repetitive themes and words/phrases are important. It doesn't (shouldn't) matter what the speech is about. It's the technique that's important. Repeat a phrase throughout the speech, sometimes several times in a row. "We shall fight on the beaches. We shall fight on the landing grounds. We shall fight in the fields and in the streets." This repetition is important to keep your audience interested.
-Put yourself into the speech somewhere. No one likes a speech from some guy talking about some thing. They want to hear about YOU. So start off with something that has effected you. "I remember, walking the streets of New Orleans the day before the storm. I saw something in the faces of my fellow citizens. We all knew something big was coming." Start with yourself, then broaden out to your topic. Get them interested in YOU and they might listen to everything else you have to say.
As for topics: Pick something that affected you, but that everyone knows about, that you broaden out. "I remember being there when Kanye stole Swift's thunder. I remember the shame we all felt. I remember..." If you want to be creative, funny, a little (lot) strange, and still have a chance at getting a good mark talk about your time in the Vietnam war or something. Yes, you weren't in the Vietnam war, but the purpose is to make a good speech, not tell people about the motorcycle you want to buy or why such and such is awesome. "I was on a swift boat, going up the Da Nang. There were snakes in the water. There were bugs in the air. There was Charlie, in the jungle." Steal some jokes from Tropic Thunder to lighten it up. Go for a Dr. Strangelove feel. It might be weird, but everyone will remember it, and unless your English teacher sucks, you'll ace it.
