You must have a valid passport to travel abroad. The process and cost associated with getting a passport can be high so start the process at least six months before you plan to leave. Different countries have different processes for obtaining a passport so contact your local government to find out the process. When entering the USA, your passport may be turned down if it expires within six months of your entry so take care of renewals before leaving as well.
A visa is permission to apply to enter the United States. Foreign citizens must apply for a visa at an American embassy or consulate abroad. Citizens of certain countries may be able to travel without a visa on the Visa Waiver Program (VWP) if they meet certain conditions. They must be traveling to the U.S. for business or tourism for a period of not more than 90 days, have a round trip ticket, and fly on certain air carriers.
For an overview of some common visa types:
B-1 or B-2 Visa- The "visitor" visa is a nonimmigrant visa for persons desiring to enter the United States temporarily for business (B-1) or for pleasure or medical treatment (B-2). To be eligible one must submit:
The F-1 student visa. To obtain a student visa you must first complete an I-20 application which states that you have financial means to support yourself and are accepted into an educational program. The United States Immigration and Naturalization Service requires all F-1 students to take 18 hours of classes per week to maintain F-1 status. When you enter the United States on an F-1 student visa, you will usually be admitted for the duration of your student status.
Employment Visas- The H1B visa may be issued to individuals who seek temporary entry in a specialty occupation as a professional. Some examples of "specialty occupations" include accountant, computer analyst, engineer, financial analyst, scientist, architect or lawyer. The petition can be approved with a combination of college or university course work plus three years work experience for each year of university education missing.
H-2B Visa allows guest workers to come to the United States from around the world to live and work. An international beneficiary who is offered a job by a U.S. employer may enter the U.S. for a temporary time of specified duration to fill the offered position. The employment must be a one-time need based upon low U.S. worker availability, seasonal, or cyclical needs.
The H-3 visa is for an alien coming to the United States to receive training from an employer in any field other than graduate education or training. This covers a specific course of job-related training that has been planned in the United States which may include employment incidental to the training period.
J-1 visa If the individual does not qualify for an H visa classification, he or she may qualify under the J-1 category. The J-1 visa can be used by any U.S. companies primarily in an entry-level position to gain work experience and training in his or her field. The primary purpose of the alien€™s J-1 visa is to improve his or her knowledge of American techniques and operation in any U.S. industry and take this experience back to their home country to utilize upon returning home. A person must have at least one year of experience or a degree in the field in order to qualify for a J-1 visa. The J-1 visa is valid for the length of time the employer requires the alien€™s services, up to a maximum of 18 months with no renewal.