If you're in the process of writing a script or planning on writing one in the near future, it's strongly recommended that you read as many scripts in your particular genre as you can. Both so you can get a feeling for the structure as well as to see how other writers turned their story ideas into a finished screenplay.
One great resource for finding sample scripts is the Internet Movie Script Database. I was literally blown away with the selection they had. These aren't reprints or transcriptions, but actual drafts of thousands of movie scripts. Be sure you add these guys to your favorites.