There's really no hard and fast rules about what a fanedit trailer must consist of. TM2YC and BionicBob are right in that a lot of great trailers give you an idea of what has changed with the fanedit. But I agree with NewSpock that not every FE trailer needs to do that, and that the main goal of the trailer is to put you in a mood to want to see the movie.
Because I'm self-indulgent I'm going to show a few more of my trailers to give examples.
Boogie Nights Extended Edition
Use of title cards to explain the changes. 20 minutes of deleted scenes are added. More cocaine, more nudity, etc.
Scream - The Giallo Cut
Says very little about what has changed. The only detail I give is that I added music from Goblin. But you
see the VHS look and you
feel how the music changes the atmosphere of the film.
Say Anything Extended Edition
Honestly this is one of my favorite trailers I've done. I tell you nothing except the title and give you just a glimpse of the movie.
So basically what I'm trying to say is that every trailer is different, there's not a checklist or guideline of what has to be in a trailer or how a trailer has to be done.
But I do have some suggestions:
1) Keep it under 2 minutes 30 seconds. Longer than that and the attention starts to wander.
2) Pick a song that ties into the movie. Don't just slap the Star Wars theme over a Transformers trailer.
3) Find the rhythm of the music and edit the images to flow with it.
4) You don't necessarily need dialogue in a trailer, but don't put in shots of characters talking when we can't hear them. SHOW, don't tell.