A classic example of this is the trailer of Love Aaj Kal, which showed everything from how Kartik Aaryan and Sara Ali Khan got together to how they fell apart. When we finally stepped into the theatre, just because we love Imtiaz Ali, the film was just a *really* long version of the trailer itself.
Secondly, stop giving away your best dialogues and punchlines in the trailer. I get it, you want to sell the film but do I want to go and watch a movie in the theatre and hear the exact same punchlines again? Spread across 30 minutes, those are the only highs in the film.
On the comedy front, the trailer of Luka Chuppi had a good set of punches and a promising comedian, Aparshakti Khurana. But sadly, the film packed its best moments into the trailer in a bid to entice the audience and left nothing to imagination. Honestly, it was just a disappointment.
Who did it right? The trailer of Shubh Mangal Zyada Saavdhan managed to get it right. It gave us the basic storyline, establishing the fact that the two male leads were in love with each other and the parents aren't happy. But it didn't tell us much about their end and how they fell in love, leaving surprise elements intact.
Add to that mix a great soundtrack which is recognisable and you've got yourself a viral trailer. Both the songs used in the trailer are old hits which weren't butchered for a change. Their lyrics aren't heard and the music adds to the vibe of the trailer instead of taking away from it.
A film like Bhoot: The Haunted Ship starring Vicky Kaushal is a horror movie that relies heavily on background music did a terrible job with it. Plus, you showed us the ghost in the first go, haunting two random people and now we have nothing left to come to the theatres for.
Overall, your visuals could be right, you could have Shah Rukh Khan or Amitabh Bachchan narrating the story but if you give me the entire storyline in the trailer, then I have no incentive left. Not to mention the absurd concept of a trailer for a trailer? No one needs a teaser telling us the day the trailer will release. Anything that can be said in an Instagram post, doesn't need a YouTube post.