The laws of lashon hara are too lengthy to include in one article. In fact, Rabbi Israel Meir Hakohen of Radin wrote an entire book about these laws. The book is also called Chafetz Chaim (which caused the author to be known as the “Chafetz Chaim”).
The name is inspired by the verse in Psalms, “Whoever of you desires life (chafetz chaim) . . . guard your tongue from evil . . .”
Nevertheless, here is a brief overview of some of the laws, mostly gleaned from Chafetz Chaim:
1. Lashon hara literally means “bad talk.” This means that it is forbidden to speak negatively about someone else, even if it is true.
2. It is also forbidden to repeat anything about another, even if it is not a negative thing. This is called rechilut.
3. It is also forbidden to listen to lashon hara. One should either reprimand the speaker, or, if that is not possible, one should extricate oneself from that situation.
4. Even if one has already heard the lashon hara, it is forbidden to believe it. On the contrary, one should always judge one’s fellow favorably.
Nevertheless, one may suspect that the lashon hara is true, and take the necessary precautions to protect oneself.
6. It is forbidden to even make a motion that is derogatory towards someone.
7. One may not even retell a negative event without using names, if the listeners might be able to figure out who is being spoken of.
8. In certain circumstances, such as to protect someone from harm, it is permissible or even obligatory to share negative information. As there are many details to this law, one should consult a competent rabbi to learn what may be shared in any particular situation.