As Seenwills experience:
- check their product lines, factories are normally display their own products;
- Check the business license.Entities with "Manufacturing," "Production," or "Processing" in their registered name are factories, while those with only "Trading" or "Sales" are trading companies;
- Check the sales' product professional knowledges;
- Ask them to present their real factory locations to visit;
- Check their brands online whether it is same as they said;
- Employ a translator or sourcing agency to help you for your negotiations;