Bring a watch!
Miscellaneous: If you're like me, you tell time not by a wrist watch or the position of the sun, but by my mobile phone. Well I couldn't get a mobile phone signal in either Zambia or Botswana, so leaving my phone on caused the battery to die much quicker (usually my mobile phone battery lasts about a week -- but there is lasted about 8 hours because it was constantly searching for a signal!)
Toiletries and Medical Supplies: Remember to take malaria pills with you. I noticed that there in fact are mosquitoes even in the city center. I even spotted one inside the National Gallery. I forgot to take mine, luckily didn't get malaria, though..
Miscellaneous: This one pictured I bought in Botswana. It's a good one because I can plug American stuff and European stuff into it.