Look
Height can wait. Write one feature recognizable at a distance and nameable in dialogue up close.
Put it in the library. Do not change hair color every chapter.
Temperament and speech
How they are in public, and how they are with you, on two lines, with the condition that switches them.
Speech is sentence length, whether they explain, and one closing habit. A sample exchange beats “cold tone”.
Only the past that causes something
One old event that changed how they act, and how it shows now. A biography with no consequence does not belong in chapter one.
The relationship with you is its own paragraph: whether you have met, what happened last time, who they think you are.
World and other people
If this is not ordinary contemporary life, write the era, what can be said, and what cannot be said in public.
Another person who matters: name, relation to the lead, and whether they are in the room. If not, say so.
CharacterMemory
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