Take the game of Clue to a new level and play it as a role-playing mystery game. Take the time to come up with clues for everyone instead of just giving the players a list of places, weapons and people. Watch the movie for ideas on what clues to use. If you are playing in a house, you can use the rooms of the house as the rooms where the crime may have been committed. If you are playing outside, you can turn it into a scavenger hunt. Get the neighbors involved to help solve the crime.
Pick your murder weapons, places the murder might have been committed and the people that may have committed the murder. The number of weapons should coincide with the number of players. You can be traditional with the weapons from the game and give everyone a prop weapon.
Decide on the murderer. The murderer will be a part of the clue game and will know that he is the murderer. The murderers job is to play the game as well and try to thwart the other players from figuring out that he was the perpetrator.
Give each player a back story complete with the details of where they were during the time frame the murder was committed. The job of each player is to convince the others of their innocence.
Make up clues to help the players figure out who the real murderer is. Hide the clues in the different rooms or outdoors if the game is being played outside. Write the clues on paper for the players to find, or with a little time and ingenuity, you can give the players more covert clues related to the mystery, such as lipstick on a napkin or a tear from someones shirt. Don't give away the mystery in the clues. The clues are only there to help the players eliminate players from the suspect list. By questioning each other, most of the mystery should be solvable.
Pick an end time where the murderer is revealed if no one figures out the answer. Give everyone has a chance to question one another and find all of the clues. Each player should have equal opportunity to try to figure out the murderer. At the end of the game, give everyone a chance to try to name the murderer before revealing who the killer was.