What are the 3 main questions you should ask for a supplier to test him and his product?

You have to make sure:

1. Can supplier provide you the quality you need?
2. Can supplier provide you the quantities you need for the certain time?
3. Can supplier provide the product for the agreed price?

1 - some names of companies or agencies the Supplier is certified by .

2 - Time needed to provide and supply the materials  .

3 - minimum accepted  amount of the down payment .

Using ISO standards one could ask regarding Quality questions which include product reliability, quantities with availability and  bench-marking question with other leading product in market which include technical specification comparability. 

1-The certificate of origin must beauthenticated bythe Foreign Ministry. 

2- inspect certificate of the productand mustconform with the specifications.

3- if it holdsISO QualityCertificate.

1- comparison sheet of the product's specifications against the required or contractual specification

2- time schedule of supplying 

3- source certificate and formal approvals

1.Request the supplies to provide  manufacturing certificate.

2.Experience of supplier  in production .

3. Time needed for supplying the product .