Citizens of the UK, the US, Canada, Australia, and most countries in the EU, need a tourist visa to enter Tanzania. Application details and forms can be found on Tanzanian Embassy web sites. Tanzanian embassies issue single ($50) and double ($100) entry visas (handy if you're planning to cross over to Kenya or Malawi for a few days). They do not issue visas for more than two entries.
Tanzanian tourist visas are valid for 6 months from the date of issue. So while planning ahead for visas is a good thing, make sure the visa is still valid for the length of time you plan to travel in Tanzania.

You can obtain a visa at all airports in Tanzania as well as at the border crossings, but it is advised to get a visa beforehand. In order to get a visa you have to have proof that you plan to leave Tanzania within 3 months of your arrival.

Health and Immunizations

Immunizations
No immunizations are required by law to enter Tanzania if you are travelling directly from Europe or the US. If you are travelling from a country where Yellow Fever is present you will need to prove you have had the inoculation.
Several vaccinations are highly recommended when traveling to Tanzania, they include:

• Yellow Fever
• Typhoid
• Hepatitis
• Diptheria

It is also recommended that you are up to date with your polio and tetanus vaccinations. Rabies is also prevalent and if you're planning to spend a lot of time in Tanzania, it may be worth getting the rabies shots before you go.

Safety
Tanzanians are well known for their friendly, laid-back attitude. In most cases you will be humbled by their hospitality despite the fact that most people are a lot poorer than you. As you travel in the touristy areas, you will probably attract your fair share of souvenir hawkers and beggars. Remember that these are poor people who are trying to earn money to feed their families. If you aren't interested then say so, but try and remain polite.
Basic Safety Rules for Travelers to Tanzania.

• Make a copy of your passport and keep it in your luggage.
• Don't walk on your own at night in the major cities or on empty beaches especially in Pemba and Zanzibar.
• Don't wear jewelry.
• Don't carry too much cash with you.
• Wear a money belt that fits under your clothes.
• Don't carry a lot of camera equipment especially in the major cities.
• Beware of thieves posing as police officers.

When to Go to Tanzania
The rainy seasons in Tanzania are from March to May and November to December. Roads become washed out and some parks even have to close. But, the rainy season is the perfect time to get good deals on safaris and enjoy a quieter experience without the crowds.

The best months to climb Kilimanjaro are January, February and September when it is warm and dry.

The best time to see the annual migration of millions of wildebeest and zebras is February to March when they have their young. The dry season (June to November) in general is the best time to go on safari in Tanzania since the animals congregate around the water holes and river banks.

The best time to enjoy the beaches of Zanzibar and Pemba is between July and October when there are less tourists escaping the European winter and there's little chance of rain.