Clothing should be neutral — khaki, olive, brown, grey. Bright white shows every speck of dust, dark blue and black attract tsetse flies, and camouflage patterns are illegal for civilians in Tanzania. Pack layers rather than warm clothes: dawn on the Ngorongoro rim can be near freezing and the same day can reach thirty degrees by lunch.
The list that matters: a fleece or down jacket, a windproof layer, long trousers and long sleeves for dusk, shorts and t-shirts for the day, a wide-brimmed hat, sunglasses, high-factor sunscreen, closed walking shoes, sandals for camp, a swimsuit, insect repellent with DEET, personal medication, a head torch, spare camera batteries and memory cards, a universal adaptor (Tanzania uses UK-style three-pin type G, 230V), and binoculars if you have them.
If your itinerary includes a light aircraft, the limit is 15 kg per person including hand luggage, in a soft bag with no rigid frame. Laundry is available at almost every camp and is cheap or included, so pack for three or four days rather than the whole trip. Leave the rest with us in Arusha.