Require the minimum that proves the stage was genuinely reached, and enforce it with validation at stage exit rather than on save. Every required field is a tax on rep time, so each one needs a report or an automation that consumes it — if nothing reads it, it shouldn't be mandatory.
Tie the requirement to a document or artifact wherever possible: a proposal link before negotiation, a signed contract before closed-won. Artifact-based gates are harder to fake than picklists and give managers something real to inspect. Publish what each gate requires so the rules are enablement, not surprises.
Every claim above comes from work LeanScale published. These are the sources.