Call ahead to reserve a campsite at Sesriem Camp.
Renting your own 4x4 and self-driving through Namibia is the best way to experience the country. Namibia has surprisingly good infrastructure given the roads are unpaved. Locals and fellow travelers are generally extremely helpful if you to run into car problems. Also, by driving yourself, you can adjust to your nugget's pace for safaris, naps and frequent stops.
Both excursions are best during sunrise or sunset, for optimal photo opportunities and avoiding the heat.
The best time to travel to Namibia is March–October. The cool air offers clearer skies and ideal photography conditions, and temperatures are milder both day and night. June–August is Namibia's winter and temperatures drop to freezing at night, so plan accordingly.