When trying to successfully download a legitimate movie on torrent sites, you need to look for 2 things.
First is the size of the file. Anything under 100mb is probably a trailer and/or soundtrack.
If you find a file that is 700mb+, you then need to read the comments. If you're looking for something like Iron Man 2, there is a chance that someone will just upload the first movie. Don't ask me why, there are many faggots in this world.
Also, check the release date on Wikipedia or something.