3. If your status as traitor has been betrayed to the rest of the server, cease mic and text chat to everyone else. It is suprisingly easy for you to get cocky if you have taken out a few attacking innocents and say something to notify others of your location.
4. As detective, BE USEFUL. Most detectives sit idly about like they are an innocent. Detectives are there to identify traitors if they get too careless and leave a body lying about with fresh DNA on it. Make sure to report to the scene of a death to see what you can learn.
Tell us something we don't know. -__-
3 is only useful if 3D mic sound is enabled in the server. If not, then it doesn't really matter if they've found you out or not.
4 is rather obvious. But most of the time, the detectives are the ones who are killed first because it's strategic to take them out first(I.E. because of armor and health stations.)