What are the best tested methods to find the potential buyers of the products you need to export? And why?

It would be advisable to hire overseas agents on a commission basis. To find reliable sales agents, you can contact the Chamber of Commerce in the country you intend to export to, the Export Promotion Councils and independent consultants..

The best method is on the ground research in target countries. Nothing beats interacting with the populace, reading newspapers, visiting markets, visiting stores. One can even place a test advert in a local newspaper and gauge the response.

Visiting embassies and ministries  is a ok idea however its not from the horses mouth ie direct from the potential customer.

It is no use to participate in exhibitions unless you know the public will like the product. Exhibitions can be deceptive in that everyone is interested there.

Before planning to export it is important to understand the destination market carefully. In my experience, I have seen that local knowledge or a visit to the destination market is very important in establishing a good rapport as well as gaining local insight. Buying patterns for a product manufactured in the home country could be very different in different parts of the world.  Purchasing habits, payment terms and packaging requirements for A product could be very different in West Africa versus East Africa, Europe Versus North America and simply the Middle East versus the Far East. 

What helps tremendously is participating in the local trade shows as an exhibitor or simply as a visitor. It gives the exporting company a great insight into a market in a relatively small period of time with a very dynamic picture of the local requirements and trends.