Here's one of my versions of a trailer:
Walt Disney Titles appear.
Caspian's Nurse (voiceover): Once, a long, long time ago, there lived two kings and two queens who ruled over all of Narnia.
(During the Voiceover)
Scenes of the coronation from LWW are shown. Fade out.
Nurse (voiceover cont'd.): With the help of the Great Lion Aslan, they defeated the White Witch, and ruled peacefully over Narnia for fifteen years.
(Still during voiceover)
Fade into scenes of Aslan's resurrection and the battle b/t the Witch. Scenes fade out and fade in to a scene of young Caspian listening to his Nurse tell him the story.
Young Caspian: But they disappeared, never to return again.
Nurse: Yes.
Fade Out. The scene fades in to another scene, this one showing King Miraz talking intently to a scared young Caspian.
Miraz: Who has been telling you all this nonsense?
Camera zooms in on Miraz's face, then Caspian's worried one. Fade out. Walden Media titles appear. Fade into a scene of an older Caspian standing atop a tower, looking out at the land below.
Miraz (voiceover): This is your new tutor, Dr. Cornelius.
Scene switches to another in which young Caspian first meets Dr. Cornelius. Fade to scene in which Dr. Cornelius and an older Caspian are stargazing.
Miraz (voiceover cont'd): He shall teach you everything you need to know as a prince.
Fade to a scene in which Dr. Cornelius and Caspian are sitting atop a tower at nighttime.
Camera zooms on Cornelius' face
Dr. Cornelius: Do you know anything about the Old Narnia?
Camera switches to Caspian's face
Caspian: Everything. My Nurse told me stories...of the Golden Age.
Fade out to scenes of the older Pevensies riding through the forest, hunting the White Stag. Fade out. Titles appear: "One summer day..." Fade into scene of Lucy walking toward the Wardrobe. Fade out. Titles appear: "Four children stepped into a world..." Fade into scene of all four Pevensies first entering Narnia together. Fade out. Titles: "...that would never leave them behind." Fade into scene of the Pevensies discovering their treasure hall one thousand years later. Fade out. Fade into scene of the children discovering their Gifts. Camera zooms in on Peter, Susan, and Lucy, one at a time, looking at their Gifts. Camera zooms on Susan last.
Susan: Wait...my Horn...it's not here.
Scene fades to one when Dr. Cornelius gives Caspian the Horn. Camera is close-up on Horn in Caspian's hands. Camera shifts to Cornelius' face.
Dr. Cornelius: Blow on this Horn...and Aslan will send help to you...although I do not know in what form it will be.
Close-up on Caspian's face.
Fade out. Titles: "On May 16th" Fade into scene of Caspian escaping from the castle on Destrier, with soldiers in close pursuit. Scene blacks out. Fade into scene of Caspian standing atop a hill, with the Horn in his hand. Fade out. Titles: "Those four children..." Fade into scene of the Pevensies falling out of the Wardrobe. Fade out. Titles: "...will return to Narnia." Scene of Caspian blowing the horn appears, and quickly shifts to Pevensies in train station.
Susan: Did you hear that? Camera zooms on her face.
Scene quickly shifts to Pevensies arriving in Narnia again.
Lucy (voiceover): Are we in Narnia again?
Scene fades to one when Pevensies are listening to Trumpkin's tale.
Trumpkin: The prince...
Scene switches quickly to Caspian falling off Destrier in slow-motion. Scene returns to Trumpkin.
Trumpkin: ...needs your help.
Scene fades. Fade into scene of Dr. Cornelius talking to Caspian atop the tower. Close-up on Dr. Cornelius' face.
Dr. Cornelius: Your uncle is an usuper, Caspian! He killed your father...now that he has a son, an heir, he wants to kill you!
Close-up on Caspian's face. Blackout. Titles: "A prince in danger..." Fade into scene of Caspian first meeting Trufflehunter, Trumpkin, and Nikabrik. Fade out. Titles: "A legacy forgotten..." Fade into scene of Caspian, Trufflehunter, Nikabrik, and Trumpkin arriving at the Dancing Lawn. Scenes of the Seven Brothers of Shuddering Wood, the Three Bulgy Bears, Pattertwig in a tree, and Reepicheep bowing to Caspian are shown.
Reepicheep: We have waited so long for this day, my Prince.
Close-up on Caspian's face. Fade out. Fade into scene where Lucy tries to wake the Trees up.
Trufflehunter (voiceover): Even the Trees have forgotten who they are...
Fade out. Titles: "A leader..." Fade into scene of Aslan atop hill meeting with Lucy, Peter, Edmund, Susan, and Trumpkin. Fade out. Titles: "Will return..." Fade into scene of Aslan awakening the Trees and shift to scene of the maenads and Bacchus dancing. Fade out. Titles: "...to save His people yet again." Shot of Aslan roaring quickly appears. Scene quickly shifts among scenes: Edmund, Peter, Caspian, Trumpkin, and Trufflehunter fighting the hag, the werewolf and Nikabrik at Aslan's How, Caspian kneeling before Peter and Edmund after his rescue, close-up of Peter saying "We will challenge him [Miraz] to a duel", and Peter fighting Miraz. Fade out. Titles: "A land that was dead" Fade to scene b/t Peter and Caspian looking out at the camp of Old Narnians.
Caspian: Do you think we can really defeat my uncle?
Peter: With Aslan we will.
Shift to scene of Aslan talking to Gwendolen at the school. Shift to scene in Miraz's tent.
Miraz: They think their fairy tales can destroy me. Last I checked, I was a real person, not some figment of imagination.
Close-up on Glozelle and Sopespian looking at each other. Shift to scene of Edmund yelling to his troops.
Edmund: FOR NARNIA, AND FOR ASLAN!
Narnians charge at Telemarines. Fade out. Titles: "Will rise to new life" Scene of Aslan and His reinforcements charging onto the battlefield appears. Various scenes are shown of Narnians fighting, including Peter swinging his sword at someone's head, Edmund in a fixed swordfight w/ a Telemarine, Reepicheep and his mice stabbing the heels of the enemy, Susan running and shooting her arrow, Trumpking and Dr. Cornelius charging at a group of Telemarines, Caspian being knocked down, and Lucy throwing a dagger at a Telemarine. Shots of each of the Pevensies faces, Caspian and Dr. Cornelius' faces, Reepicheep lifting his sword, the maenads dancing, and Aslan smiling shift very quickly from one to another. Blackout. Title appears: "The Chronicles of Narnia: Prince Caspian"
Dr. Cornelius (voiceover): You never know when the fairy tales you believe in might be true.
Fade out title. Fade in "May 16, 2008". Fade to credits. Fade out.