Instructions
Set up your murder mystery. Assign each person you'll invite a name and a roll in the game, including the murder victim and the murderer.
Send out the invitations. The invitations include the information each dinner guest needs, including what Clue character they play during the murder mystery game, and any behaviors they need act out. A profile might call for a player to act rich and snotty, or disheveled and drunk.
Decorate for the party. Select items that fit the time period and type of murder mystery game you've chosen. Choose music that fits the theme of your party.
Introduce each guest as they arrive. Even if the people know each other, they won't know which character each is portraying.
Order different guests off on different errands throughout the house to give everyone time away from everyone else. It will be during one of these excursions that the murder occurs and another in which the murder is discovered. Guests can try to hide the facts; but if confronted, they cannot lie.
Gather everyone together at the end of the party and ask each person to solve the murder mystery. Take time to let each person squirm under the spotlight. Let everyone have a turn until the mystery is solved.