Start here. This is the direct spoken answer to practice first.
Overview
Chunk size is a retrieval decision: small units improve precision, while larger units preserve context.
I start from the document's natural structure, such as headings, paragraphs, procedures, or table rows, and keep each chunk within the embedding model's input limit. Chunks need enough surrounding context to stand on their own but should not mix unrelated topics. I choose size and overlap using representative retrieval queries rather than copying a universal token number.