Read the book first, then see the movie. That way, after the movie, I can moan and cry how the movie deviated from the actual plot of the book and how none of the characters in the movie were protrayed as they were in the book.
Or if you're a lame, watch the movie, then read the book. That way, you can think how GREAT the movie was and you won't be disappointed. Then you read the book and realize that the book is so much better than the movie. Win-win situation, amirite?