short analysis.

The trailer begins with a voice over before the action begins on screen. There is a slight delay, as on screen we see a long shot of Tyler and Megan's wedding. The voice over then clearly states that she began from the wrong point of the story and rewinds the footage on-screen.
A diagetic bell, although added during editing it comes through the narrative, cuts off the female voice and introduces the audience to a normal school day. We see Tyler and Charli, hand in hand, walking into the classroom. A match on action is used with the over-the-shoulder shot of Tyler and Charli entering, as they walk past Megan who is seated.
We then cut to a mid-shot of Megan arriving at Charli's house for prom. Outside this house, we cut to seeing Megan say on the kerb, looking at her watch as a car's reverse lights ignite and move from the back of the shot to the foreground. Music then accompanys the footage in the text.
We cut to Megan talking to a stuffed cat about her problems, as she imagines that it has had an accident on her shoe. The atmosphere is dark, suggesting night time and a dark event to come. Her diagetic voice clearly says that nothing ever changes.
We cut to Charli reaching for the cat in the tree, and falling on the floor. A shot of the sky and streetlights, twirling around is shown to immediately tell the audience that she has fallen out of the tree. The music is cut as screams take its place. They echo and a mean laughter is heard.
A scene in the hospital, with dreary mise-en-scene as they're waiting for the news. This makes the audience feel uncomfortable in the place, and expect the worst. As the doctor approaches an over-the-shoulder, shot-reverse-shot conversation between the doctor and Tyler begins, about the death of Charli.
The two characters left, Megan and Tyler, comfort each other in a two shot where Megan moves in to kiss him. We jump to a parallel scene of later that night where she is using the exact same move. The audience clearly know he didnt refuse at the hospital otherwise they wouldn't have ended up in her room together. Tyler rises this time, from the two shot on the bed, and moves towards the door. We cut time out here as he is leaving in the morning. We know there is a time change because the mise-en-scene is lighter, suggesting sunlight filtering in through the window. A shot-reverse-shot is used for the coming conversation between Tyler and Megan.
Tyler leaves the room and an establishing shot of the church is shown, with text stating that we're taking 3 years out of the story and skipping to the future.
The long-shot that we saw at the beginning of the trailer returns and the story continues from where Sarah left off with the voice-over before. There is no music since the death of Charli, and her return evokes the return of music also. As she pops out from behind the vicar, we get a lively, upbeat tune occuring.
As Megan steps back from the vicar, the audience are left to guess that she doesnt marry Tyler at that point in the movie. Tyler then throws a 'hissy' fit and requests confetti being thrown on him. The voice is in slow motion, and is deeper than usual for comedic effect. The mid-two shot of Tyler and Sarah allows us to mostly see him, and the confetti being pushed his way. The music fits with his 'huff' and creates a laughable moment for the audience.
The text then cuts to footage that is white tinted, suggesting an eerie atmosphere. This is used to show that Charli is a ghost and it is easy to distinguish the difference between her when shes alive and dead. The white effect connotes imagination, similar to effects in some movies when the screen waves from side to side to suggest daydreaming/dreaming/imagining. The music which is accompanying the '3 years later' part of the trailer is very unrealistic and suggests, to me personally, the idea of a gameshow or fun.
After the fight between Megan and Charli, we fade to Tyler being dressed up. The mid shot of him getting dressed misses off his head, suggesting that he's embarrassed. This shot could also be a POV shot from Charli's point of view, as she watches to make sure he puts on the dress which she's forced upon him. This then cuts to a long-shot of Tyler lay on the bed with Charli in the background, giggling. He has clearly been forced to spend time in a dress. Megan walks in, and looks twice at the sight she is faced with while laughing silently to herself.
We then cut to a cuddling session on the sofa, between Tyler and Megan. A long shot of Charli, as she walks in, is shown and we flick back to the cuddles on the sofa. Tyler moves from Megan and we return to Charli, who has walked out of the room and returned with crisps. This connotes the awkwardness of having a ghost around.
We then, finally, fade to a black screen where the title is revealed. The voice over takes over, declaring that the only way to find out what happens is to visit the cinema in the summer, 2010.

california sunshine and tennessee rain, i'm an east coast kid with a west coast way. i don't mind the weather, but i hate the way it has to change...