I usually include the following in my GM/DM binder:
A piece of paper on which I keep track of the group's AC, attack bonuses, passive perception scores, and other conditions/abilities affecting or having been granted to the player characters.
Session notes, including story outlines, maps, encounters, locales, dungeons, etc.
Homebrew monster statblocks.
Tables upon tables of homebrew rules, elements of the economy, and other setting details.
The setting '(b)ible'.
We keep records of what the group has done on Discord, and, I like to carry a tablet or laptop around for audio and the occasional visual effect.
A piece of paper on which I keep track of the group's AC, attack bonuses, passive perception scores, and other conditions/abilities affecting or having been granted to the player characters.
Session notes, including story outlines, maps, encounters, locales, dungeons, etc.
Homebrew monster statblocks.
Tables upon tables of homebrew rules, elements of the economy, and other setting details.
The setting '(b)ible'.
We keep records of what the group has done on Discord, and, I like to carry a tablet or laptop around for audio and the occasional visual effect.