The purpose of movie trailers is to entice the general public in to see your movie. It should grab the attention of the viewer and make them interested in learning more, in discovering the full story and, ultimately, giving you their cash in ticket prices or sales.
It should not reveal, or appear to reveal the entire story. The trailer for The Martian contains a scene from the climax of the book. Now, admittedly, maybe it's only obvious to me because I had read the book, but still. The trailer for Terminator: Genisys has a major reveal! I was warned in advance, and loved the twist when I saw it in theatres. But, as Honest Trailers point out, that's nothing new for the Terminator franchise. Only watch this if you've seen both T2 and Genisys.
As a matter of fact, as a viewer, I've learned to stop watching trailers once I'm hooked. I only watched that first trailer for The Martian, and I really enjoyed it, despite having previously read the superior novel. As mentioned, Genisys was a really great experience in the cinema, a lot of fun, even if it was only an okay movie, but mostly because I hadn't seen the trailers.
Once I've decided to see a movie, I'm pretty much done with trailers. It sometimes take more than one, but more often than not, the first real trailer is enough to get my attention. I've only seen that first, "Chewie, we're home" trailer for the Force Awakens and avoided screenshots, additional footage and any or all talk about it. I'm looking forward to seeing this on a big, big screen, with the best quality surround sound. I'm going to enjoy going in almost completely unspoiled and coming out, hopefully, with a smile on my face.
But I'm not nearly as excited for the Force as I am for a Civil War. This. Just this.
Done. Completely, utterly done. No more trailers, no behind the scenes, no photos from the set, and definitely no "exclusive footage". I'm already excited. I don't need any more.
Roll on May, 2016!