You must work together and form bonds and listen very carefully to what people say. Together you vote to hang whoever seems the most suspicious. Random killing is not recommended.
You vote to kill one person per night, you all start out knowing who the other mafia members are. Finding out who is a roled townie is paramount if you are to succeed in your continued secret infiltration and internal destruction of the city!
Psychic (Roled Townie)
Each night you can sorta "see" someone's true identity. You see townies, roled townies, or mafia.
Coroner (Roled Townie)
After every night phase, you get the names/roles of those who died. Additionally every other night you can view any of the bodies of dead members to see if you notices anything different about them.
Masons x2 (Roled Townie)
You start out with a small, but prebuilt alliance, because you know each other
Guardian (Roled Townie)
Every night, he chooses 1 person, it can be anyone, to 'protect', this person will be saved if the mafia tries to kill him.
Night Watchman (Roled Townie)
you only work one out of every four nights but you always spy a dark cloaked figure in the night, unfortunately you can only tell small insignificant random pieces of information about them... fortunately its almost guaranteed that said figure is a mafia member.
Hitman (Roled Mafia)
Once every three nights the Mafia can opt to use this member and kill a person regardless of their protected status. By sheer luck this member kills because the mafia doesn't know who is protected... or so the townies should hope.
Mob Spy (Roled Mafia)
No matter how many times the psychic "views" this mafia member or the coroner works on him, he always comes back as townie or roled townie, the key to catching this slippery fiend is to see if status changes when viewed and you only get a 50% chance of having it change whether s/he is alive or dead.