The Kosi Bay border control post is the best point of entry when crossing into Mozambique from South Africa. There are a few documents/ rules which you must have with you before you’ll be allowed over the border. http://www.borders.sars.gov.za/KwaZuluNatal/Kosi%20Bay.htm

1. Valid passport
2. Third party insurance for your vehicle with a R150 import fee
3. A towing licence for your trailer, boat, wet bikes etc R80
4. Permission in writing from your insurance company proving cover in case of accident etc
5. South Africans DO NOT need a visa to enter Mozambique. Non SA Nationals can purchase a visa at the border for around R180.
6. Your vehicle, caravan, trailer need to have a ZA sticker on it. This should be in view and within 150mm of your back licence plate.
7. When towing in Mozambique you need to display two yellow triangles on a blue background. The one must be on your front right bumper and the other on the back of whatever you are towing.
8. You also need to have a reflective jacket when driving in Mozambique.

There may be other rules so its best to have a chat to border control, the details can be found at the above link.