We refer to the official public information of the U.S. Department of State that provides the guidelines for the guest worker visas, as follows:
The Immigration and Nationality Act provides several categories of nonimmigrant visas for a person who wishes to work temporarily in the United States. There are annual numerical limits on some classifications which are shown in parentheses.
H-1B classification applies to persons in a specialty occupation which requires the theoretical and practical application of a body of highly specialized knowledge requiring completion of a specific course of higher education. This classification requires a labor attestation issued by the Secretary of Labor (65,000). This classification also applies to Government-to-Government research and development, or co-production projects administered by the Department of Defense (100);
H-1C classification applies to foreign nurses coming to perform nursing services in medically underserved areas for a temporary period up to three years. The Nursing Relief for Disadvantaged Areas Act of 1999 (NRDAA) has been reauthorized for an additional three years, and will expire on December 20, 2009. To learn more about the reauthorization of the H-1C program, see Department of Homeland Security, U.S. Citizenship and Immigration Services Press Release.
H-2A classification applies to temporary or seasonal agricultural workers;
H-2B classification applies to temporary or seasonal nonagricultural workers. This classification requires a temporary labor certification issued by the Secretary of Labor (66,000);
H-3 classification applies to trainees other than medical or academic. This classification also applies to practical training in the education of handicapped children (50);
L classification applies to intracompany transferees who, within the three preceding years, have been employed abroad continuously for one year, and who will be employed by a branch, parent, affiliate, or subsidiary of that same employer in the U.S. in a managerial, executive, or specialized knowledge capacity;
O-1 classification applies to persons who have extraordinary ability in the sciences, arts, education, business, or athletics, or extraordinary achievements in the motion picture and television field;
O-2 classification applies to persons accompanying an O-1 alien to assist in an artistic or athletic performance for a specific event or performance;
P-1 classification applies to individual or team athletes, or members of an entertainment group that are internationally recognized (25,000);
P-2 classification applies to artists or entertainers who will perform under a reciprocal exchange program;
P-3 classification applies to artists or entertainers who perform under a program that is culturally unique (same as P-1); and
Q-1 classification applies to participants in an international cultural exchange program for the purpose of providing practical training, employment, and the sharing of the history, culture, and traditions of the alien's home country.
In order to be considered as a nonimmigrant under the above classifications the applicant's prospective employer or agent must file Form I-129, Petition for Nonimmigrant Worker, with the United States Citizenship and Immigration Services in the Department of Homeland Security (USCIS). Important Note: It is very important for prospective employers to file the petition as soon as possible (but not more than 6 months before the proposed employment will begin) to provide adequate time for petition and subsequent visa processing. Should you need petition processing faster, see Premium Processing Service on USCIS website. Once approved, the employer or agent is sent a Notice of Action, Form I-797, the notification of petition approval. However, the I-797 is no longer needed for the visa applicant's interview, since petition approval is now verified in the Department of State's system called Petition Information Management Service (PIMS). In order to verify the petition approval, we will need your approved I-129 petition receipt number so please make sure to have this available. It should be noted that the approval of a petition shall not guarantee visa issuance to an applicant found to be ineligible under provisions of the Immigration and Nationality Act.
PIMS Processing Update: Important information for prospective employers and visa applicants, when extension of stay, change of status or petition amendment has been requested.
The USCIS and the State Department have agreed to a process that will facilitate the entry of nonimmigrant petition-based employment visa petitions (H, L, O, P, Q) into the State Department’s Petition Information Management Service (PIMS) system, where an extension of stay, change of status, or petition amendment is requested. Upon approval of a petition where a change, extension, or amendment is requested and the petitioner provides duplicate original petitions to the USCIS with original signatures on all forms as would otherwise be done for consular notification, the USCIS will send the duplicate copy to the State Department’s Kentucky Consular Center (KCC) for scanning and entry into the PIMS database. Persons are encouraged to identify the duplicate petition with a brightly-colored cover sheet and to mark on it “Please send this copy to KCC upon approval.” Therefore, if there is any chance that the beneficiary will need to obtain a visa at a US embassy or consulate after a change, extension, or petition amendment, it is advisable to file a duplicate petition set with original signatures on the forms.
Visa Ineligibility / Waiver
The nonimmigrant visa application Form DS-156 lists classes of persons who are ineligible under U.S. law to receive visas. In some instances an applicant who is ineligible, but who is otherwise properly classifiable as a temporary worker, may apply for a waiver of ineligibility and be issued a visa if the waiver is approved.
Applying for a Visa
Applicants for temporary work visas should generally apply at the American Embassy or Consulate with jurisdiction over their place of permanent residence. Although visa applicants may apply at any U.S. consular office abroad, it may be more difficult to qualify for the visa outside the country of permanent residence. As part of the visa application process, an interview at the embassy consular section is required for visa applicants from age 14 through 79. Persons age 13 and younger, and age 80 and older, generally do not require an interview, unless requested by embassy or consulate. To make an appointment for interview you will need to provide the receipt number that is printed on the approved Form I-129 petition. The waiting time for an interview appointment for applicants can vary, so early visa application is strongly encouraged. Visa wait times for interview appointments and visa processing time information for each U.S. Embassy or Consulate worldwide is available on our website at Visa Wait Times, and on most embassy websites. During the visa application process, usually at the interview, an ink-free, digital fingerprint scan will be quickly taken. Some applicants will need additional screening, and will be notified when they apply.
For current fees for Department of State government services select Fees.
An application, Nonimmigrant Visa Application, Form DS-156, completed and signed. The DS-156 must be the March 2006 date, electronic "e-form application." Select Nonimmigrant Visa Application Form DS-156 to access the electronic version of the DS-156.
A Supplemental Nonimmigrant Visa Application, Form DS-157 provides additional information about your travel plans. Submission of this completed form is required for all male applicants between 16-45 years of age. It is also required for all applicants from state sponsors of terrorism age 16 and over, irrespective of gender, without exception. Five countries are now designated as state sponsors of terrorism, including North Korea, Cuba, Syria, Sudan, and Iran. Select Special Processing Procedures to learn more. You should know that a consular officer may require any nonimmigrant visa applicant to complete this form. Here is Form DS-157 .
A passport valid for travel to the United States with a validity date of at least six months beyond the applicant's intended period of stay in the United States (unless country-specific agreements provide exemptions). If more than one person is included in the passport, each person desiring a visa must make an application.
As part of the visa application process, an interview at the embassy consular section is required for almost all visa applicants. The waiting time for an interview appointment for applicants can vary, so early visa application is strongly encouraged. During the visa interview, an ink-free, digital fingerprint scan will be quickly taken, as well as a digital photo. Some applicants will need additional screening, and will be notified when they apply.
One (1) 2x2 photograph. See the required photo format explained in nonimmigrant photograph requirements .
To schedule the interview appointment, you will need the receipt number that is printed on the approved Form I-129 petition. NOTE: During your interview, the consular officer will use the receipt number to verify the Form I-129 petition approval. Therefore, Form I-797 is no longer used to verify petition approval, and is no longer necessary for your visa interview. With the exception of the H-1 and L-1, applicants may also need to show proof of binding ties to a residence outside the United States which they have no intention of abandoning. It is impossible to specify the exact form the evidence should take since applicants' circumstances vary greatly.
Entering the U.S. - Port of Entry
A visa allows a foreign citizen coming from abroad, to travel to the United States port-of entry and request permission to enter the United States. Applicants should be aware that a visa does not guarantee entry into the United States. The Department of Homeland Security, U.S. Customs and Border Protection (CBP) officials have authority to permit or deny admission to the United States. If you are allowed to enter the U.S., the CBP official will determine the length of your visit on the Arrival-Departure Record (Form I-94). Since Form I-94 documents your authorized stay in the United States, it is very important to keep in your passport. Upon arrival (at an international airport, seaport or land border crossing), you will be enrolled in the US-VISIT entry-exit program. In addition, some travelers will also need to register their entry into and their departure from the U.S. with the Special Registration program. The Department of Homeland Security, Customs and Border Protection internet site offers additional information on Admissions/Entry requirements.
With the exception of "Q-1 Cultural Exchange Visitors," the spouse and unmarried, minor children of an applicant under any of the above classifications may also be classified as nonimmigrants in order to accompany or join the principal applicant. A person who has received a visa as the spouse or child of a temporary worker (a petition-based NIV), may not accept employment in the United States (with the exception of spouses of L-1 visa holders - L-2 spouses may engage in employment with an "employment authorized" endorsement or appropriate work permit.) The principal applicant must be able to show that he or she will be able to support his or her family in the United States.
All of the above classifications have fixed time limits in which the alien may perform services in the United States. In some cases those time limits may be extended by USCIS in order to permit the completion of the services. Thereafter, the alien must remain abroad for a fixed period of time before being readmitted as a temporary worker under any classification. USCIS will notify the petitioner on Form I-797 whenever a visa petition, an extension of a visa petition, or an extension of stay is approved under any of the above classifications. The beneficiary may use a copy of Form I-797 to make an appointment to apply for a new or revalidated visa during the validity period of the petition. The approval of a permanent labor certification or the filing of a preference petition for an alien under the H-1 or L classifications shall not be a basis for denying a visa.
Questions about filing a petition, qualifications for various classifications, or conditions and limitations on employment should be made by the prospective employer or agent in the United States to the nearest USCIS office. Questions about filing a visa application at a consular section abroad should be addressed to the appropriate consular office abroad. Inquiries about visa cases in progress overseas should contact the appropriate U.S. Embassy or Consulate handling your case.
Source: http://travel.state.gov/visa/temp/types/types_1271.html (with cuts)