If a Mafia member is on trial and most likely will be voted guilty, it may not make much sense to vote innocent. Doing so will expose you as Mafia immediately, especially if you are one of very few people to vote innocent.
Likewise, being the only one to not vote a confirmed Mafia to trial can be almost as bad as voting innocent.
It is highly recommended to AVOID say each others names at night on the chance that there may be Spy in the game who could be listening to Mafia chat.
In some cases, using false names may causes confusion among the Town people (see: WIFOM).
One advanced tactic if the Mafia has a Janitor is this: If a Mafia member is sure to be killed at night, have the Janitor target that Mafia member. This will make it so that the Town doesn't see his role and thus leaving them with no information.
Consiglieres should be careful about revealing themselves as Investigators, make sure it's possible for there to be more Investigators, and that people don't happen to have died in the same order as your clues.