Most visitors should apply for a B-2 visitor visa at the U.S. Embassy/Consulate in order to enter the U.S. as a tourist. Review the Department of State site for more information on this type of visa.
However, some individuals may be eligible to enter the U.S. on the Visa Waiver Program instead.
Parents and siblings of people in F-1 or J-1 status are not eligible for F-2 or J-2 status. Forms I-20 and DS-2019 are not issued to invite parents, parents-in-law, or siblings. If you wish, you may send your relatives a copy of your I-20 or DS-2019 form, but they should not submit it to the consular officer unless asked for it. Do not send your original I-20 or DS-2019 to your parents, other non-dependent relatives, or friends. You should keep the form yourself. If you wish to invite your spouse or children, please review Inviting Your Spouse and/or Children to the U.S. 
What documents do my relatives need to obtain a B-2 visa? ISSS recommends that your relatives take the following documents with them to the U.S. consulate:
The length of a visitor’s initial permission to stay in B-2 status is determined by the officer at the port of entry. The maximum initial period is six months. People who want to remain longer need to apply for an extension . There is no specified limit on the number of extensions allowed. Be aware that the USCIS requires at least four months to process an application for extension in B-2 status. That does not mean your visitors need to apply for an extension four months in advance. Their obligation is to make sure the USCIS receives the extension application before their current stay expires.
The Visa Waiver Program allows visitors from certain countries to visit the U.S. for pleasure or business up to 90 days without a visa. For a complete list of participating countries, please visit the Department of State site. Visitors must meet certain requirements  to participate in the program. Eligible visitors do not need to visit a U.S. consulate and apply for a visa prior to vising the U.S. Visa waiver travelers will instead be required to register their travel plans in the Electronic System for Travel Authorization (ESTA) a minimum of 72 hours prior to departure.
Individuals who enter the U.S. on the Visa Waiver Program are not eligible to change status; nor may visitors apply for an extension of their stay beyond 90 days. Individuals who previously experienced visa denials or who believe they might be ineligible for a visa should contact their local U.S. embassy or consulate prior to traveling on the Visa Waiver Program.
Be sure your visitors have health insurance that will cover them while in the United States. Most guests will require “major medical coverage,” which is health insurance that goes into effect if they are unexpectedly hospitalized as a result of an accident or an illness. Most local healthcare providers in the Iowa City area do not accept foreign health insurance plans. Without coverage, your guests could experience financial devastation if hospitalization becomes necessary.
All visitors in B-2 or WT status who entered the U.S. are restricted from enrolling in a degree program. Such enrollment will constitute a violation of status and could result in serious consequences. It is also extremely difficult for visitors in B status to change to F-1 status while in the U.S. If you have a relative who is considering the possibility of applying for a degree program in the U.S., please contact an ISSS adviser for information on the best course of action to be taken, preferably before they come to the U.S.
No, visitors in B-2 status or WT (Waived Tourist) status may not work in the U.S. during their visit.
In 2004, visa officers at U.S. consulates and immigration officers at U.S. Ports of Entry began gathering "biometric" data. This data is collected when persons apply for both non-immigrant and immigrant visas and upon entering and exiting the U.S. Biometric data, in this case, simply refers to the photographs along with digital "inkless" fingerprints. This information is kept electronically by the U.S. government, and is included in the SEVIS tracking system. The intent of the U.S. government is to have an electronic tracking system of non-citizen's entries and exits to and from the U.S.
One thing ISSS wishes to point out to students and scholars and their visitors is that precise entry and exit information will be kept electronically. This means that anyone who "overstays" his or her visit to the U.S. will have that information immediately available to immigration officers. If you have visitors come in B-1 or B-2 status, or who may come on the Visa Waiver program, remember that they are allowed to be in the U.S. only until a specific date (usually 6 months, but sometimes less), which is stamped in the passport upon entering the U.S. If the B visitor does not leave the U.S. by that date, they will be considered to have "overstayed" the visit to the U.S. (unless steps were taken to extend their visit before that date). Consequences of overstaying a visit to the U.S. may vary from a "review with immigration officials to removal from the United States or even a bar from future entry, depending on the individual circumstances."