The most common mistake I see in screenplays is that the plots just aren't good enough. There are unlimited variations on the basic plots, but rarely do we get a truly original story such as Memento, Little Miss Sunshine, The Sixth Sense or The Usual Suspects.

Screenwriters often struggle to find a good plot twist because they keep looking at the structure as if moving scenes around will magically transform the script into something better. This is often true, but just as often, the writer may be looking in the wrong place.

Often the best way to give your plot a fresh twist is to imagine your characters in a situation that may never make it into the script but will force them to act. One of my favorite exercises is to consider what would drive a main character to commit murder.

This technique allows you to see your characters in a new way.

Consider what the film, Memento (directed by Christopher Nolan), would have been like if the hero, Leonard (Guy Pearce), had been an obvious villain. There would have been no suspense and the plot, even told backwards would have been predictable. It was the choice of an unexpected character, not the structural gimmick that made this film feel fresh and original.

Even if your script is about characters who kill for a living, asking yourself why they chose this as an occupation in the first place can yield useful insights that can create depth to even the most archetypal cop, killer, soldier or hit man.

Dr. David Buss, an evolutionary psychologist conducted a set of studies that investigated the underlying motives and circumstances of murders, conducted a highly detailed study of nearly 400 murders, the most extensive study of homicidal fantasy ever conducted. Dr. Buss says: "Killing is fundamentally in our nature because over the eons of human evolution murder was so surprisingly beneficial in the intense game of reproductive competition," and that "Our minds have developed adaptations to kill, which is contrary to previous theories that murder is something outside of human nature-a pathology imposed from the distorting influences of culture, media images, poverty or child abuse.

In one of Dr. Buss' studies, in order to determine what would drive people over the edge and cause them to kill, participants were presented with more than a hundred different scenarios in which they recorded the probability they would kill. "Nearly all people express a willingness to kill in some circumstances-to prevent being killed or to defend their children from killers," Buss said.

Finding the answer to this question of what could drive your main character to murder can be the one question you need to answer to make your screenplay "pop."

The best part is that identifying the homicidal moment for your characters can work well whether you're writing a drama or a comedy. In the drama, The Godfather II, Vito Corleone, as a young man becomes capable of murder in order to save his family when the local Mafiosi takes away his job. Before that event he is shown as a gentle man. In the comedy, Little Miss Sunshine, Richard Hoover (Greg Kinnear) becomes so angry with his agent, Larry Sugarman (Gordon Thompson), that he wants to kill him, but instead does some crazy things to get his daughter to the Beauty Pageant. If he hadn't become so enraged, we would not have been able to believe that he would really steal his father's body from the hospital.

Imagining a situation where your main character would commit murder can lead you to a better, more original story.