The U.S. State Department has a database on its website (travel.state.gov) with visa requirements for each country in the world, the U.S. embassy and consular offices, security information and medical conditions. Knowing the needs of the country is particularly important if you plan to enter the country as a tourist and plan to stay a while. The State Department's website includes a list of required vaccinations for each country as well.
Get a visa at the Embassy, Consulate or designated office in the country you are visiting. Most applications require you to provide your passport and a recent photo glued or stapled to the application. The specific information that must be included in the application includes your name, passport purpose of your stay and the duration of your stay.
Submit your application and the required fee, in agreement with the instructions of the embassies. Some embassies allow you to post requests for revision; others require that you submit your application in person.
Wait for your acceptance. Processing times vary embassies. The waiting time is as fast as four days for some countries or as long as two to four weeks for others.