The dunes at Sossusvlei require more than a day to truly appreciate. Unfortunately we only had a morning. As we weren't staying inside the park the earliest we could enter was 6:30 AM. This meant a pretty early morning as we were more than 45 minutes away. The light is already gorgeous by the time the dunes are in sight, but you know the good light will fade fast so there is a sense of urgency. I didn't get to spend the time I wanted photographing the early sun on the dunes as we knew if we wanted to get to dead vleibefore it got hot and the light got bad, we had to hurry. This is where two mornings would be good. One morning to photograph the dunes, one to head out to dead vlei. You have to be driven in by an operator - they don't allow private vehicles, and there's a bit of a hike over the dunes ones you get there.
Once you climb the last dune you'll see dead vlei down below, and it's not exactly what you might expect based on pictures you've seen. It was bigger then I expected and there's a lot more people then I expected. It's also very hot, even in winter, even at 9 in the morning. If the light had stayed nice I could have spent hours here. It's truly amazing. A can't be missed stop in Namibia.
In the afternoon we visited Sesriem Canyon. While I didn't find it nearly as spectacular as Dead Vlei, it was interesting. Since most of it is below ground level, Sesriem Canyon is a nice respite from the Namibian sun.
It was a very long day but well worth it. Photographically, it was mostly what I expected. A tripod is a good thing and bring something to protect your gear - if there's a breeze you don't want all that sand getting all over your gear. A word of advice, don't bother trying to keep the sand out of your shoes, though. You can't stop it from happening and the sooner you accept it, the sooner you can move on!