Board Tips
You can move your playing piece through any open or closed doorway. Never count entering the doorway as a move. Using a secret passage does not end your turn. It simply ends the physical movement of your playing piece across the board. If both corner rooms belong to you, go back and forth between them until you find the suspect and the weapon.
Luring Strategy
Lure another player into a room by waiting for the player in question to come to you. This strategy eliminates the need to roll the die to get them into the room. If you notice other players trying to use a luring strategy, obstruct their efforts. Draw their attention to a decoy room, or transfer them from room to room alongside your playing piece.
Process of Elimination
The process of elimination helps bring the correct scenario to light according to the enthusiasts at the Games Information Depot. Every time a card appears, assign it a number or letter on the game's detective pad. For example, a player might inquire with Susan about Colonel Mustard with the pipe in the library. If Susan has one of these cards, mark your pad with an "S1" for Susan and "1" item. If she has none, mark with "SX." No matter what sort of code you use, your notes will eventually eliminate options.
Accusations and Suggestions
Never make an accusation unless you are positive of its validity -- a false accusation costs you the game instantly. Focus on deducing the room of the crime, often the most difficult element to determine, from the beginning of game play. You can make an accusation from any room on the board, but you must leave and re-enter the room to make a new suggestion.