Passport, visa, required vaccination certificate, international driver's permit... paperwork is paperwork, it has to be done. When organizing a trip to Tanzania it's easy to be caught up in thoughts about safaris and forget about the necessaries - visa, shots and so on. Remember that before you'll be let loose on Tanzanian soils, you'll have to meet certain requirements.
A visa is required for virtually all non-Tanzanian nationals; check this out in advance. If you apply for a visa from your country of origin, then your passport needs to be valid for a full six months after your departure date. You need to attach the following to your application: a photo, a hotel or agency reservation, a copy of a return plane ticket. If you fill in your form at the Tanzanian Embassy, you'll get a visa within 3 days, if you apply by post it will take 7 days. Visas are valid for 3 months. The cost is 50€ - roughly 50USD and 80$Ca
A yellow fever vaccination is required for entry. It needs to be done no later than 10 days before you leave. Although not obligatory, it's wise to take malaria tablets and get any other recommended vaccinations.
You can apply for a visa on arrival at Dar es Salaam's airport. It works out a lot cheaper than if you apply from another country. A customs officer will gather together all tourists, take their passports/documents and visa application money - all of which is given to controllers for verification. You'll then have a 15 minute or so wait. The pile of passports will come back and with a smile and a "Karibu", the customs officer will have welcomed you in Swahili! Now that business has been taken care of, you'll be ready to start your Tanzanian adventure.
Bear in mind your vaccination certificate will be scrutinized. An up to date yellow fever vaccination is oligatory - no shot, no entry.
A word about hiring cars/vehicles. Your driver's permit from home may not be enough. Some car hire agencies will require an international permit, which you can usually get for free in your home country.