Documents first
Collect company registration, tax registration (GSTIN in India), export codes where relevant (IEC), and factory address proof. Verify that the entity you contract with is the entity that produces.
Capacity and machinery
Ask for a machine list, line count, workforce size and current order load. Stated monthly capacity should be plausible against machinery — a factory with twenty machines cannot credibly offer very large monthly volumes in complex garments.
Samples reveal process
Commission a paid sample against a written specification. Evaluate stitching quality, measurement accuracy against the size chart, and how the vendor handles comments. Responsiveness during sampling predicts behaviour during bulk.
Subcontracting policy
Ask directly whether the vendor subcontracts, and require written disclosure if any process (embroidery, washing, printing) is outsourced. Undisclosed subcontracting is a leading cause of quality failures.