Two of the security officers at Zanzibar airport asked for a tip from the departing tourists when they were checking the hand luggage at the x-ray machine. And some tourists gave money because they felt commited to do so.
Unique Suggestions: It creates an unethical business if tourist pay money to officials for nothing. Be aware of this and say no.
It's easy to let one of the workers carry your luggage for you. And the workers will ask the tourists for that, without saying what it cost. Many tourists believe the service is included because of the high price for the ferry ticket. A Norwegian couple did that, and I saw their surprised faces when the workers claimed 10000 Tanzanian shilling (10 USD) for each luggage after they were onboard. They really felt fooled, but didn't say anything. Be smart and carry your own luggage.
The Tanzanian people are so friendly and nice, but when stupid tourists pay more than a day salary for almost nothing it creates an unethical business.
In Dar and in Arusha, I was disappointed how bad I fared with bargaining (I am actually good at it, you see). The Tanzanian male shopkeepers offer higher prices to tourists.
Unique Suggestions: Best thing to do is to start with half the price they quote then just leave when you are not happy with the last price.
The reason why they still managed to sell at the price they liked and not much at the price I liked is because they make serious faces and you think they really meant that they do not make profit with your price. Later I learned that they're good actors.
"Slipway mall" is a bit isolated from other shops and public places in Dar es Salaam. So it's easy for the taxi-drivers to overcharge the tourists. It cost 2-3 times more to leave the place than it cost to get there. The taxi drivers say it's a fixed price, but they know that you are dependent on them because of the distance to town.
The ferryport in Dar es Salam is busy. Beware that you have to wait in an open transit hall with no aircondition before you can enter one the many ferries to Zanzibar. It is hot and not enough seats for everybody. Especially not in the week-ends.
It may be smart to buy a ticket in advance and enter the ferryport 15-20 minutes before depature.
every taxi driver you walk past is likely to ask you for a taxi, regardless of if you are in front of your accomodation or just stepped out of a taxi. It does become annoying at times or you can simply laugh it off or like me offer the taxi to the street touts knowing to well they are going to refuse it.
taxi from airport to town not more than about 10,000 max if you are white (mzungu) and otherwise you can probably bargain with them more. People are going to be very friendly with you, and most have good intentions, believe it! But then there are sometimes some others who want money, and if you are ok with it it doesn't hurt to give a little for something like carrying your bags, but don't take out a fat wallet, just if you have some change, maybe 100, 200 or at the most 500 for a simple service. Just use your common sense and you'll be fine.