The Shrieking Shack??
The Shrieking Shack maybe? I think that's Ron and Hermione in the foreground there.

The Knight Bus
The Knight Bus swerving through traffic.

Some random choir
A choir singing "Something wicked this way comes" throughout the trailer. Since when is there a choir at Hogwarts?

Boggart Snape walking out of the wardrobe
Boggart Snape walking out of the wardrobe towards Neville and the class.

Lupin and Neville
Golly gee, look at our Neville (Matthew Lewis)!! And Lupin (David Thewlis) doesn't look as terrible as I expected.

Boggart Snape transforming...
This is truly a must-see! It's Boggart Snape transforming from the Riddikulus spell.

Boggart Snape as Grandma Snape!
And the result! Snape (Alan Rickman) in a dress. Well...Neville's grandmother's clothes...

'Have you seen this wizard?'
The Sirius poster in Hogsmeade. He's turning around and screaming (or maybe laughing?) around him.

Hermione and Ron on the train
Hermione (Emma Watson) and Ron (Rupert Grint) on the train towards Hogwarts. Obviously, the dementor has entered...

This is a cat. Yeah. A CAT!!! Is that not the creepiest cat you've ever seen? What have you done, Hermione?!?

Harry and Snape in a corridor
Harry (with the Marauder's map?) and Snape (with a lit wand) in a corridor

Mr. Weasley and Harry
Mr. Weasley making Harry promise not to go looking for Sirius Black in the Leaky Cauldron (to which Harry replies "Why would I go looking for someone who wants to kill me?")

Sirius in the Shrieking Shack?
Sirius pointing at someone/something in the Shrieking Shack (?)

Harry doing homework in bed
Towards the beginning, Harry does his homework under his sheets in bed during the summer break.

The trio (seemingly minus Ron) running down a path
Harry and Hermione running down a path

The trio hiding behind a wall of pumpkins
The trio staking out Hagrid's hut

Hagrid keeping control!
Hagrid, probably during Care of Magical Creatures class, while the class runs away. Maybe he's taming a Hippogriff?

Harry in Dumbledore's office
Harry doing a spell in Dumbledore's office. Maybe it's a patronus?

A dementor entering the Hogwarts Express
The hand of a Dementor opening a window on the Hogwarts Express.