Ask where production happens
A supplier may coordinate sourcing while a manufacturer is closer to cutting, stitching and finishing. Ask which stages are handled in-house and which are outsourced.
Ask how quality is controlled
Clarify when checks happen, who signs off on finishing and how issues are handled before dispatch.
Ask about repeatability
A useful partner should be able to document article, fabric, sizing, branding and dispatch details so a successful run can be repeated.