Try to experience local events that are happening- live musicians, markets which usually happen weekly. Be sure to interact with the local people and learn from them.
Taxis are the main form of travel in Namibia. You can get a taxi for very cheap and it will take you within a certain distance for a set price, instead of a metered cost by mile. If you want, you can buy out a taxi or fill it with 4 people. Otherwise, you may be sharing the taxi with some strangers. I did not have any issues with taxis, but we were often in a group.
Etosha National Park was an incredible experience where we saw lots of wildlife. It is well-known for a reason.
If you can make it to the Namib Rand International Dark Sky reserve in the Namib Desert, I would recommend it. The stars there are incredible and we even saw some shooting stars. Take the chance to see the stars like never before.
In Windhoek, there is a viewing platform called 3 circles where you can see the whole city. There are concrete walls with local graffiti and an expansive view.
Dune 7 in Walvis Bay is the tallest dune in Namibia. Take the chance to hike up it. This is best done barefoot and beware bringing a digital camera because the wind whips the sand around on the top and could scratch your lens.
Try the food! There is a local staple called pap that is eaten with meat. It is a white cornmeal substance that pairs well with dishes of meat mixed in flavorful sauces. I loved trying the different types of meats, particularly types of antelope-type animals, Kudu, impala, springbok. I also tried a local delicacy of the mopane worm. Don't be afraid to try new things! If you have dietary restrictions, you can find food that works with your diet. Just be sure you are clear in asking what dishes contain.
Figure out how and where you're going to travel. Namibia is a vast country, so plan beforehand which sites you want to see most and decide if you are going to rent a car or find some other mode of transportation.
Whether it is for study abroad or for a trip, I would highly recommend taking the chance to visit Namibia with its beauty, contrasting landscapes, and wonderful people.