Write It Out
List the characters, facts and speculative opinions that are revealed. Writing down or highlighting clues as they appear helps you keep track of important information. Be sure to take notes that reflect which characters are directly involved. For example, when playing the board game Clue, the possible suspects are limited by the numbers of kids playing the game. Update this list as the game continues to ensure you have the most information possible. If you list possible solutions to the mystery, be sure to write down the reasons you believe each are true. Do not erase solutions as they are disproved, add the reasons you were wrong to your list to ensure you do not return to the same solution later.
Talk It Out
Bounce ideas among a group of friends. Sometimes talking about the mystery game will make the solution clear. Recite the mystery plot and clues to the group. Avoid omitting information you deem unimportant, one of your assistants may discover a relevant connection you missed. If you do not want your friends to solve the mystery for you, be sure to tell them you are not looking for input, but talking through the problem.
Compare and Contrast
When you become familiar with the plot and process of a particular mystery game, you can rely on past experience to solve the mystery. Often, players will reuse a comfortable strategy every time they play. (e.g., they will always place their most valuable cards to the right of the board, they will always bluff) If playing alone or against a computer, try to recall games with similar mysteries to inform your decision. For example, when playing role-playing games on the computer, suspect characters who are overly helpful.
Educated Guess
Making an educated guess can put you much closer to the solution of a tricky mystery. Using the clues given, comes up with a way the event could have occurred. For example, if you are trying to figure out why the floor of a crime scene is wet you might list various ways water could have been introduced. (e.g., water could have been poured on the floor intentionally, it could have spilled, an ice cube could have melted).