Estimate how much film you'll need, then bring twice as much. Film is hard to find. Bug repellent, sunscreen, a well-ventilated hat. Get the best pair of binoculars you can afford or borrow, and a heavy-duty but lightweight flashlight. You don't need serious hiking boots, but your shoes must be comfortable enough to walk in for hours.
Weather varies from cool mornings to brutally hot afternoons to cold nights.
Bring clothing you can layer. Free laundry service is offered daily at most lodges and camps. Dust is omnipresent, so keep filters on your lenses. Zambian currency is pretty much useless everywhere but in Zambia. Lodges will take U.S. dollars.