A taxi from the airport should cost around 15,000 TSH (at 1,220 TSH = $1). If you rent the taxi for 5 hours, try to negotiate for 40,000 /= to 50,000 /=. It takes about 20 - 30 minutes from the airport to the city center depending on the day and traffic. Airport taxis have a fixed rate to the city center and the various hotels. There's a sign there indicating the prices, and they won't fluxuate from those prices to get you to the city center. Don't be afraid to walk away from one and talk to another one who knows that you walked away from another taxi. Another way of negotiating would be to take an airport taxi to the City Center and on the way negotiate for the 5 hours. If you can't get a good price then take it to the New Africa hotel, there's always a bunch of taxis sitting across the street and one of them will be hungry. Taxis are available just as you exit the arrivals, they should be obvious.

This information was based on the forum thread:

http://www.tripadvisor.com/ShowTopic-...