Adding Journal Entries - LunarNeil/Call-of-Cthulhu-Campaign GitHub Wiki
Investigators can add any information they want to their Journal, no matter how trivial. Transcripts of dialogue between characters, scribbled theories, clues, secrets written in code, even the unnatural symbols and chants used in arcane rituals are all good things to note.
The only requirement is that the player specifically mention when they are taking notes. Moderators are not required to "play back" any conversations for you once they have occurred, or to assume your character can remember information that you have forgotten. If you don't want to forget something, take a note, and add it to the Journal before you lose it. Once information has been added to the Journal it is very difficult for the Moderator to claim your character has forgotten it.
When the player chooses to add an item to the Investigator's personal notes, many times the Moderator will hand the player an index card with a brief summation of the information written on one side. This card can be kept in a folder, taped to a page, or kept with the Journal in any way the player chooses. So long as the player can produce the card, the Investigator counts as having the information in their Journal.
Many times the information isn't given on a card or piece of paper the player can keep, requiring the player to record it themselves. Sometimes a useful clue may not even be identified specifically by the Moderator, it may just come up in conversation with another character. The accuracy of the information they transcribe depends on how well the player listens and writes it down.