What I learned
1. When you have a list of potential victims, don't contact them all at once. Track them down one at a time, so the killer can keep one step ahead in killing them off.
2. When there's a large set full of armed actors, crew and directors and a crazy guy comes in and stabs someone, everybody, I mean every single person, runs away, completely emptying the place, except for the one guy he's after.
3. When faced with a maniacal killer who has killed your friends, police, and possibly your girlfriend, don't kill him when you have the chance. Even save his life a couple of times while fighting him. After all, you want a fair fight, even if it is a battle to the death.
Other than that I enjoyed the movie.