You have to have a concept that can be explained (and comprehended) clearly in a few sentences. It helps if you put it in terms of movies that have already been made ("It's like King Kong meets The Godfather.") Plan to describe your concept in terms you would use if you were talking to 8th graders. Don't get too elegant with your language. And remember: you probably will get only 2-5 minutes to hook them, so don't waste too much time getting ready to describe the concept; the meeting might end before you get to it. You have to be able to confidently sell it and explain how it will appeal to the 18-35 year-old males who are the main people who pay to go to the movies. You DON'T need a finished script. You MAY need to write out a "treatment," defined on Wikipedia as "a piece of prose, typically the step between scene cards (index cards) and the first draft of a screenplay for a motion picture. It is generally longer and more detailed than an outline (or one-page synopsis)." A really tough thing is coming up with the idea. Even tougher is getting a meeting with someone you can pitch it to. It helps to know someone whose name you can drop to get in the door. Good luck!