The Rules Of Mafia

Introduction
The concept behind a Mafia Game is basically a game of two teams. One team is the Mafia. These are a group of players who all know who each other are and it is there job to survive and not to be found out to be Mafia. The second group is the Innocents, these are the rest of the players. It is there job to find out who the Mafia are. Now Innocents do not know who other Innocents are, so it is the Mafia's job to convince the Innocent that they are also Innocent.

Day Time
During Day Time, the whole town discuss who they think are Mafia and they have the option to lynch off a player who they believe to be Mafia. All the Innocents (along with the Mafia) get one vote each and once a majority is reached (over half the amount of players) that person is then killed off and there alignment and role is revealed.

Night Time
During the Night Stage, players PM the Moderator of the game with there actions they can make (see role thread). The Night Stage is also important as it is when the Mafia kill off an innocent. Once all roles are in, the Moderator writes up the killings and often leaves clues (and maybe red herrings too) for the Innocents to try and work out in order to get a good lynch during the day time.

Number of Mafia
A game with just one more Innocent player than Mafia players during the day phase will be won by the Innocents if they always kill Mafiosi (otherwise they lose). A game starting with a night kill must begin with at least two more Innocents than Mafiosi to permit an Innocent victory.

The optimal number of each type of character depends on players' preferences for game length and Mafia win percentage. A good rule of thumb is about one Mafia for every two non-mafia members. So one Mafia member for under five players, two Mafia for five to seven players, three Mafia for eight to ten players, and so on. For greater than sixteen players, games usually last too long and the dead become restless. It can add excitement to conceal how many Mafia are playing (narration: "either two or three mafiosi are amongst you").

Generally, fewer players result in fewer turns and thus less time to determine the identity of the Mafia. The inclusion of "variant" characters typically decreases the Mafia's chance of victory. For example, the addition of a Sheriff or Doctor will decrease the expected Mafia win percentage.

Allowing the Townspeople to abstain from killing on certain turns can decrease or increase the Mafia win percentage as can variants which make it more difficult for the Mafia to achieve a kill (e.g. requiring them to agree on a victim independently). The "no kill" variant compensates to some extent for the disadvantage given to odd numbers of townspeople. Otherwise, 2n+1 Innocents are less likely to win than 2n Innocents (for n>2) because they have decreased their odds of voting for a Mafia each turn without increasing their number of turns (resulting in ties rather than Mafia majorities).

How to win?
The game ends either when the last Mafia member is killed (Innocent victory) or the Mafia members equal or outnumber the Innocents during the day (Mafia victory). The Innocents have no way of voting off Mafia members at this point, but the Mafia can still kill each night. Other variants have different victory conditions.

Variants
There are many different twists you can add to the game and one main one is the emergence of either a second Mafia group or Individuals. Individuals are only out for themselves and can only win if they are the last one standing.

I credit this whole thing to ThunderMan from wrestlingforum.com. I hope he doesn't mind that I have used it, as it is only for a little while before I find the time to write one of my own.