Decide how you want to obtain your visa. If you are a citizen of the United States, visiting Sri Lanka for tourism purposes, you can obtain a thirty day visa upon arrival in the country. If you are not a United States citizen traveling for tourism purposes -- or would like to apply for your visa ahead of time -- you can download an application online and mail it in.
Show evidence of return transportation -- and sufficient funds to finance your stay -- at the Embassy of Sri Lanka, if you decide obtaining a visa upon arrival in Sri Lanka works best for you. Obtaining a 30 day tourist visa is free, and if you wish to extend your visa, you can do so in Sri Lanka as well. The maximum tourist stay in Sri Lanka is 180 days.
Download and print the Sri Lanka Tourist Visa Application from a reputable website such as, Sri-lanka.visahq.com. Fill out the application accurately and completely.
Obtain an original, signed, United States passport, two passport type photographs, a copy of your confirmed airline tickets or itinerary and a copy of a recent bank statement. This must show that you have sufficient funds to travel while in Sri Lanka. You also need a personal letter addressed to the Embassy of Sri Lanka, explaining the purpose of your trip, and detailing your plans while in the country.
Mail the application to the Embassy of Sri Lanka in Washington DC. The visa application generally takes two to fifteen days to process.