Before RFQ
Clarify whether the requirement, drawings, sample evidence and supplier-facing language are ready.

Each chapter turns a sourcing stage into buyer-side control points: what to clarify, what evidence to request, and what should remain provisional until checked.
The guide is most useful when it is read at a commitment point: before RFQ, before deposit, before shipment or before repeat order.
Guides are not a replacement for project work. They are preparation material for RFQ scope, supplier evidence, sample gates, landed-cost checks and repeat-order control.