What has to be agreed before the first carton is packed.
Fix the inspection standard and the accepted tolerance
Confirm packing, polybag, carton marking and barcode placement
Agree the inspection point: in-line, final random, or both
Confirm port, incoterm and shipping marks
Collect the documents your customs broker will ask for
None of these five are published in the source catalogue. That is normal for a knitwear catalogue, and it is exactly why they belong in the first email rather than the last one.

55% Acrylic, 45% Cotton
Autumn/Winter · View style
100% Cotton
Autumn/Winter · View style
90% Cotton, 10% Lurex
Autumn/Winter · View style
100% Acrylic
Spring/Summer · View styleLead times are not published in the source catalogue. Ask for the sampling lead time and the yarn lead time separately, because the second one usually sits outside the factory.
For development: a tech pack, a measurement chart with every point defined, the intended fibre content and the care label you plan to print. For catalogue selection: the item numbers and the quantity.
Put it in writing on both sides. A sealed counter sample plus a written tolerance is what makes a later inspection meaningful.
Sample cost and sample lead time are not published. Ask for both in the same message as the quotation request.
Send what you have: a tech pack, a chart, a photo or just a list of item numbers. The first reply will tell you what is missing.