Be A Nerd - Just Sit Very Still, Don't Move Or Even Twitch
The Chofetz Chaim in his hakdama, lists 17 Lavin that you can be oveir with Lashon Hara. One of the them is Lo Sachanifu, do not flatter the sinners. By flattering and giving support to someone doing something inappropriate you become an accomplice to his crime.
When someone speaks Lashon Hara to you or before you, by agreeing with him or adding to what he said you are oveir Lo Sachanifu. Even if you only nod your head in approval you are oveir. This is especially important to remember when you are sitting with a large group. When Lashon Hara is said there is intense social pressure to chime in and show agreement with the consensus. Yet Chazal tells is that it is better to be a fool in the eyes of people (i.e., social nerd) our whole lives, rather than to be a Rasha before Hashem for even a short moment.
"Zachor Eis Asher Asa Hashem L'Miriam BaDerech B'Tzaischem MiMitzrayim"
The Ramban and other Rishonim count, among the Mitzvos Aseh Min HaTorah, the mitzva of remembering and saying with your mouth each day what Hashem did to Miriam when she spoke about her brother Moshe. The Chofetz Chaim in Shaar Tvunah Perek 12 says that being Mikayem this mitzva can save you from the aveira of Lashon Hara. More than just saying the pasuk, says the Chofetz Chaim, one must think about the incident in order for it to have its intended effect. Listen to our Shemiras HaLashon Yomi in our audio section. Two halachos a day according to the Luach. www.revach.net/audioarchives.php