What to Wear
In general, tourists should wear modest or conservative attire, especially in Zanzibar, which is a conservative Muslim society. Western women should not wear clothing that reveals too much skin. 'Kangas', brightly-colored wrap-around cloth, are affordable, available throughout the country, and can serve as a discreet covering.
The Masai people, with their colorful clothing, are tempting targets for any tourist with a camera. However, they expect to be paid for it, and you should always ask before taking pictures.
It is common practice among Swahili-speakers to use 'shikamoo' (prounounced 'she ka moe' and literally meaning, 'I hold your feet') when greeting elders or superiors. The usual response from an elder will be 'marahaba'. In Zanzibar, the equivalent of 'shikamoo' is 'chei chei'. The traveler will get along very well when using these verbal expressions of respect. In addition, a title after the 'shikamoo' is also a useful indicator that you are not just a dumb tourist -- 'shikamoo bwana' for the gents, and, when addressing a female elder, 'shikamoo mama'.
Tanzanians will also comment if you are doing any work while they are not, with the phrase "pole na kazi". It literally means "I'm sorry you have to work". A simple "asante", or "thanks", will suffice in reply.
Many Tanzanian sellers are persistent and, ordinarily, a simple head shake, accompanied by "asante sana", should settle it. However, as a last resort, a firm "hapana", meaning "no", will do the trick. Tanzanians find the word "hapana" quite rude, so please don't use it casually -- only as a last resort. Whatever you plan to do, do not tell someone you will come back to buy from them later when you have no such intention; better to be honest and say 'no' than having to avoid someone for days. They somehow have a funny way of finding you when you promised to visit their stall or shop!
The most polite way to refuse something is to say "sihitaji" (pronounced see-hih-tah-jee)- "I don't need it".