Well you certainly need not only luck, but good skills and convinction too. If you are a town power role, you need to make people believe you and advance in the direction of your choice. If you are mafia, you also need to do the same, just in wrong direction. If there are any trolls around either kill then or try to make then useful to you. If you are the role that must troll in order to win (such as Jester and Executioner) then you need to come with such a good lie, that people will actually believe you and not treat you as a Jester or Executioner.

Let me show you example. This is the face you usually show to the town as the Sheriff or any other investigative role:



If you are Mafia or neutral scum, then you MUST keep the same face you usually show as the Town lead. If you get excited too much and attract too much attention then town will get suspicious and think of your face like that:



And then you will probably get lynched or killed at night. This is a long talk, so just tell me what roles you still need to win in SC2 mafia and then ask some pros for advice. Or check Mafia wiki. Good luck!