When I watch a movie trailer, I watch it first to enjoy it, and then afterwards I analyze it. Even though I worked at a movie trailer house for a few years, deconstructing trailers is what really took my editing to the next level.
These are the primary elements I analyze in trailers:
The Music Transitions
Music transitions are usually the first thing I pay attention to. Music editing is one of the most important skills a good trailer editor has, because it's how the bones of the trailer are formed. It's one thing to take one music cue and use it for the entire trailer, but the ability to take multiple pieces that are uniquely suited to each section of the trailer opens up a world of possibility.
I went a surprisingly long time as an editor before I really made a concerted effort to pay attention to music transitions in trailers. Very rarely do music cues go directly from one to another, usually one will stopdown, and then a new one will start fresh. My fan trailer for Uncharted 3 is the first trailer I cut for the purpose of mimicking transitions I observed in movie trailers I analyzed.
Cutting to the Beat
I've watched enough trailers to know that more often than not, trailers cut to the beat of the music or match actions to the beat. And yet, every time I watch a trailer that is musically driven, I tap my fingers to the beat just so I can pay attention to where the edits or actions land on the beat.
This isn't just with action trailers set to epic orchestral music or rock music either. Trailers for serious dramas still cut on the beat. Just look at this trailer for Joy.
Accents are quick shots that are sprinkled throughout the trailer to keep things exciting. I also sometimes refer to accents as the punctuation of the trailer. They're a little burst of excitement to keep the trailer punchy.
Pay attention to what happens in between lines of dialogue, because most will have an accent in between them. Common accents are montages of guns being loaded or car gears being shifted followed by hitting a gas pedal. It could be something as simple as a door closing or just a series of shots with some sound design for emphasis.
Accents like these are very much part of the visual language of modern trailers, and their presence is one of the first signals to me of a good trailer editor. The need to accommodate accents is what makes me choose the line of dialogue that fits perfectly between two musical accents, or makes me re-edit the music so that the line is done right before the next big beat.
I'm always amazed at how you can take one story, filter it through different trailer editors, and receive totally different directions from each. What intrigues me the most is how you can say a lot about the story with just a few lines of dialogue that aren't necessarily exposition heavy info dumps. The audience can be very good at filling in the gaps of a story if you just nudge them in a certain direction, so I'm always aiming to tell more with less. Whenever dialogue for a story I'm familiar with is edited in a way I never would've thought of, I try to understand what they are doing that my instincts don't tell me to do.
The Sound Effects
Trailers usually have plenty of hits, rises, whooshes, swishes, drones, and other sound design elements. Even though I've done sound design for several trailers, I still pay attention to how other editors use those same elements. One reason is to get new ideas, and the other reason is usually just to reassure myself that I'm on the right track with my own trailers.
Mapping out a trailer
Sometimes when I'm feeling insecure about my own narrative trailer editing style, I'll download a trailer I really like, then map out where the dialogue, sound effects, and musical accents are. I already know that my editing is fundamentally similar to the trailers I admire, but it gives me some reassurance.
For example here's how I mapped out a trailer for Life is Strange (which had fantastic trailers!). By doing this, I can see that the trailer follows the lesson I was taught oh so many years ago that everything in a trailer should butt up against each other. Watch the trailer alongside my map to see how the elements fit snugly together. Each marker indicates the most prominent element during each section of the trailer.
Creating the map of a trailer is one of the best ways to really analyze the nitty gritty of the editing. By placing markers on all of these elements, you're really forced to pay attention to the construction. I've even considered reverse engineering a trailer by putting filler clips on a timeline to represent the shots, sound effects, and music clips.
So that's what is going through my head when I really want to sit down and analyze a trailer. I hope this will help you appreciate their construction and/or make trailers of your own!