Why start a unit of study with a movie trailer?
They are just an engaging start to a new unit. My middle school students love them and actually clap when they are over. The music builds excitement and they get a preview of what's to come. 

How do I make them?
I use iMovie. It's super easy to use especially using iMovie trailer templates. The hardest part is figuring out what I want the trailer to say. But I just stick to the standards and I'm able to come up with the key phrases. I insert movie clips and images related to the topic. Kids want to make them too so I've had them make a trailer at the end of a unit focusing on the key elements.