What is the most cost-effective way to send a parcel of clothes - new and used - to Nigeria. Is there a tax or duty required once it arrives in Nigeria?

You cannot mail used clothes to nigeria period. I found that out the hard way, but if you go on Nipost customs you can look it up. They specifically say no used clothes, no used shoes.

You want send EMS via usps with the top rated insurance ! Its very expensive ! I would never ever mail to nigeria without that insurance since my i had a box stollen that the postal man advised me on the i bet didnt even leave USA IT WAS STOLLEN!