I honestly went into this without knowing ONE single thing about the plot. I had only read reviews from movie forums raving about how amazing this movie is. They were spot on. This IS, by far, one of the VERY BEST sci-fi movies I have ever seen in my entire life. If you can help it, try not to watch any trailers because they will spoil a great deal of the movies (don't most trailers?)
If you HAVE to watch a trailer, watch maybe the first 30 secs just to see the characters and the main intro to the story. The best intro I can give without spoiling anything is this: A group of friends with various story lines gather for a dinner. That night, a comet is passing overhead. Things start to go CRAZY. Some people have this stereotype that sci-fi is simply robots/aliens/..flying sharks...etc. This has nothing to do with such. It involves science, and it is fiction; sci-fi. Please take the time to watch this movie. To interest you even further, I can say (again without spoiling anything) that these actors/actresses were given a guideline of things to talk about, character backgrounds and points they needed to bring up. No full blown scripts; just a general guideline. Things that happen in the movie as far as their reactions are completely genuine. It's intimately shot, and it fits this movie so perfectly. I hope you enjoyed it just as much as I did. I continue to watch this every so often, and I always seem to catch something I didn't the previous time. I LOVE IT!