Lashon Hara - General Guidelines (from Halachipedia)

It’s forbidden to speak about anything negative about a fellow Jew even if it’s true. This prohibition is called Lashon Hara. When communicating something false about another person, an even more severe sin is committed, that of Motzei Shem Ra (lit. producing a bad name for someone else). ^[3]
Rechilus / רכילות, comes from the Torah commandment "לא תלך רכיל בעמיך" / "don't be a talebearer in your nation" (Vayikra 19:16); the word "רכיל", literally "peddlar", refers to one who "carries stories" and 'peddles' them from one person to another, and says: "such and such ___ said", "such and such I heard about ___" ^[4]. Even if this is true, and there is no denigration, this speech violates a negative commandment, is a severe sin, and causes souls of Jews to be killed ^[5].
It’s equally forbidden whether one volunteered or if one was asked for information where one will come to say Lashon Hara or Avak Lashon Hara. One should not listen to one’s father or Rabbi to say Lashon Hara or Avak Lashon Hara. (See circumstances where it is permitted in section Toelet). ^[6]
Even if taking upon oneself not to speak Lashon Hara will cause one to sustain financial loss such as the loss of one’s job (such as where the employer is very immoral and irreligious and considers one who is careful about this prohibition to be a fool and he’ll fire that person), nonetheless, it is forbidden to speak Lashon Hara. ^[7]
Even if it will cause one embarrassment not to say Lashon Hara one may not say Lashon Hara. ^[8] Needless to say, such a heroic moral stance is rewarded exponentially, in line with the rabbinic dictum "Reward is in proportion to the effort."^[9]
This prohibition includes any communication that is verbalized, written, or simply implied even in a silent manner.^[10]
Even if while saying Lashon Hara one also degrades oneself it’s still forbidden. ^[11]