Please Say/Whisper The Words Out Loud
Lesson 1
If you say something to someone, and s/he didn’t hear you properly, be careful not to insult them. Some people are in the habit of saying things like "what are you, deaf or something". Yes, there are some people who are hard of hearing and could be very offended by this. You never know. Try to get peoples attention in a less offensive manner.

Lesson 2
It is important to know that we are not allowed to speak lashon hora about a Jew to someone who is not Jewish. Besides speaking lashon hora, it can cause a chilul hashem (desecration of Gd) and is liable to cause the Jew great harm. Additionally, speaking badly about one Jew can help build the stereotypes about Jews as a whole and foster antisemitism.
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Lashon Hora = Saying a derogatory/negative statement about someone else that is TRUE
Motzi Shaim Ra (Defamation of Character) = Saying a derogatory statement that is FALSE
About Whom is it Forbidden to Speak Lashon Hora - Any Individual Jew - Alive or not, - adult or child, family member (spouse, in-laws, parent, child, siblings), groups/sects of Jews, Entire Jewish Nation
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These lessons are derived from a few books:
Guard your Tongue: Adapted from Choeftz Chaim by Zelig Pliskin
The Power of Words by Zelig Pliskin
Chofetz Chaim: A Lesson a Day - The Concepts and Laws of Proper Speech Arranged for Daily Study By Shimon Finkleman and Yitzhok Berkowitz
Purity of Speech: A short lesson on the halachot of shmirat Halashon
Chofetz Chaim - A Daily Companion: Arranged by Reb Yehuda Zev Segal