Move the meaning, not just the rows.

Agree what each row represents before cleaning or importing the file.

A person, an organization and a possible purchase are different records with different lifetimes.

Start with fields that change an action or prevent a mistake; leave decorative data out.

Use fields for comparable answers, tags for meaningful membership and notes for context.

Keep an unchanged input and a separate working copy so a mistaken transformation can be explained.

Choose awkward representative records before sending the full contact list.

Decide which identifiers are reliable and who resolves ambiguous matches; a shared name is not enough.

Treat a role mailbox as an organizational contact point rather than evidence that two people are the same.

Compare intended records, actual changes and important relationships before allowing the next batch.

Name the final source, freeze period and exception owner so two systems do not become competing truths.

Give each system a specific temporary role and a dated exit test.

Preserve decisions and obligations before importing a large archive of low-value commentary.

Require the evidence needed for the next commitment, not every field at initial contact.

Train on one real-shaped fictional journey and make recovery part of the lesson.