This is your responsibility as the requirements are determined by your nationality / passport you hold. While most nationalities can obtain visas on arrival, this is not set in stone. It is best that you contact the nearest Embassy or Consulate to confirm your entry requirements and obtain your visas.
You will be travelling in a high risk malaria area and must take malaria tablets with you. A Yellow Fever vaccination is required by law when travelling to Tanzania. You must obtain this before you arrive in Africa.
A great resource is www.projectvisa.com