Bring real scenarios to a software demo: a part delivery, a credit customer, a cashier handover, a stock difference and an incorrect posted transaction.
Ask who can perform each action and what happens when it fails. Review the effect on stock, accounting and the evidence left behind.
Discuss onboarding, data preparation, branches, users and support arrangements. Agree the included scope and price in writing. A platform should fit your business rules, not persuade you to bypass them.