Visitors from the US and some other countries require visas (best arranged in advance) when visiting Brazil, Bolivia, Paraguay, Suriname and Venezuela. Make sure you have enough blank pages in your passport, and that it will be valid for six months beyond your proposed entry date to each country.
Customs vary slightly from country to country, but you can generally bring in personal belongings, camera gear, laptops, handheld devices and other travel-related gear. All countries prohibit the export (just as home countries prohibit the import) of archaeological items and goods made from rare or endangered animals. Avoid carrying plants, seeds, fruits and fresh meat products across borders.
Make sure your passport is valid for at least six months beyond the projected end of your trip and has plenty of blank pages for stamp-happy officials. Carrying a photocopy of your passport (so you can leave the original in your hotel) is sometimes enough if you're walking around a town, but always have the original if you travel anywhere (never get on a bus leaving town without it).
Visas are sometimes required, or in some cases other charges must be paid, for example for reciprocity fees or tourist cards.
Some travelers – including those from the USA – may require visas to enter several countries, including Bolivia and Brazil. Arrange these well in advance of your departure. Some countries don't generally require visas but may require a reciprocity fee (such as the $117 fee Chile charges to Australian travelers), paid upon arrival. If no visa is required, a tourist card is issued upon arrival. See individual countries for more details. Suriname charges U$35 for a tourist card, available upon arrival if flying in; if coming overland, get this from a Surinamese embassy before heading to the border.
Carry a handful of passport-sized photos for visa applications. Hold onto any entry-exit cards you are given. There can be serious fines and complications if you lose them!
If you need a visa for a country and arrive at a land border without one, be prepared to backtrack to the nearest town with a consulate to get one. Airlines won't normally let you board a plane for a country to which you don't have the necessary visa. Also, a visa in itself does not guarantee entry: you may still be turned back at the border if you don't have 'sufficient funds' or an onward or return ticket.
Onward or Return Tickets
Some countries require you to have a ticket out of their country before they will admit you at the border, grant you a visa or let you board their national airline. The onward or return ticket requirement can be a major nuisance for travelers who want to fly into one country and travel overland through others. Officially, Peru, Colombia, Ecuador, Venezuela, Bolivia, Brazil, Suriname and French Guiana demand onward tickets, but only sporadically enforce it. Still, if you arrive in one of the countries technically requiring an onward ticket or sufficient funds and a border guard is so inclined, he or she can enforce these rules (yet another reason to be courteous and neatly dressed at border crossings).
While proof of onward or return tickets is rarely asked for by South American border officials, airline officials, especially in the US, sometimes refuse boarding passengers with one-way tickets who cannot show proof of onward or return travel or proof of citizenship (or residency) in the destination country. One way around this is to purchase a cheap, fully refundable ticket out of the country and cash it in after your arrival. The downside is that the refund can take up to three months. Before purchasing the ticket, you should also ask specifically where you can get a refund, as some airlines will only refund tickets at the office of purchase or at their head office.
Any ticket out of South America plus sufficient funds are usually an adequate substitute for an onward ticket. Having a major credit card or two may help.
Sufficient funds are often technically required but rarely asked for. Immigration officials may ask (verbally or on the application form) about your financial resources. If you lack 'sufficient funds' for your proposed visit, officials may limit the length of your stay, but once you are in the country, you can usually extend your visa by producing a credit card or two.