As a general rule, most countries require passports to be valid for at least 6 months from the date of entry.
U.S. Passport Service Guide:
How to Obtain a U.S. Passport - U.S. Passport service guide
Find a passport office near you - U.S. Passport office information
U.S. Passport expediting services - how to get passports fast
Depending on your country of residence some countries require foreign visitors to obtain visas in advance. Other countries will issue a tourist visa upon arrival at the port of entry. It will depend on your citizenship and what countries you are visiting. The following website is a good reference - VisaHQ.
For U.S. citizens, visas must be obtained in advance in order to enter Brazil and Paraguay.
Brazil - Citizens of Australia, Japan, Canada and USA can now apply online for a Brazilian visa. Ready in 5 days, valid for 2 years, only US$44.24. Click here for official details and how to apply.
Paraguay Visa – A Tourist Visa is required for citizens of United States of America to enter Paraguay. A visa can be applied for online or directly at a Consulate of Paraguay. U.S. citizens can also obtain a visa on arrival in Paraguay for a stay of up to 90 days. This is ONLY available at Silvio Pettirossi International Airport in Asunción (ASU) and the fee of US$160.00 (as of June, 2018) must be paid IN CASH. Entry via any other airport or land border crossing requires a visa in advance. Passport must be valid for at least six months from the date of your proposed entry into Paraguay. Passport MUST contain one blank visa page for the visa to be issued.
Bolivia - For U.S. citizens, a visa is required to enter Bolivia. The visa can be obtained in advance or at most border crossings. Passports must be valid for at least six months from the date of your proposed entry into Bolivia. One blank passport page is required for entry stamp. U.S. citizens traveling to Bolivia for tourism must apply for a visitor’s visa, which is valid for 10 years. With this visa, you may stay a maximum of 30 calendar days per trip, not to exceed 90 days total per year. You can apply for a Bolivian tourist visa through the Bolivian consulates in the United States, Bolivian consulates in any other country and, under certain circumstances, the land and airport port-of-entry offices of the Directorate General of Immigration in Bolivia. U.S. Embassy La Paz is aware of reports of U.S tourists receiving Bolivian visas issued by Bolivian Immigration authorities at the port of entry, but the U.S. State Department does not advise relying on this option.
The visa fee is US$160 (as of March, 2016). Ensure you have crisp bills in the exact amount (change may not be made). In addition to the visa fee you must present a visa application form with 2 4cm x 4cm color photographs (with white background), a passport valid for at least 6 months from the date of entry, travel itinerary issued by your tour company (Lost World Adventures and our local tour partner in Bolivia will provide this), proof of economic solvency (credit card, cash, or a current bank statement), and an International Vaccination Certificate for yellow fever.
Arrival by land: Some tourists arriving by land report that immigration officials did not place entry stamps in their passports, which causes problems at checkpoints and upon departure. Make sure you get entry and exit stamps from the Bolivian authorities every time you enter or leave Bolivia.
We recommend printing and completing the form prior to arriving at an overland port-of-entry.
Have small bills in your cash supply for tipping. Some vendors are reluctant to give change on larger bills.