Before exporting a product sample an exporter should also know the Government policy and procedures for export of samples.
While sending a product sample to an importer, it is always advised to send samples by air mail to avoid undue delay. However, if the time is not an issue then the product sample can also be exported through proper postal channel, which is cheaper as compared to the air mail.
Extra care should be taken in order to avoid the risk associated in sending a costly product sample for export. Secrecy is also an important factor while sending a sample, especially if there is a risk of copying the original product during export.
First of all it depends on your deal with the buyer. If he asks you to send him a sample of your product and if the value of this product is high you can request him to make a payment for it. Also, in many countries, there are government financial assistances to send sample products to foreign countries. A lot of people do it outside Export Portal, but it is wrong and unsafe. I recommend you to do it with the help of Export Portal.
Good luck!