After you get the visa, you should follow several steps for a trouble free trip.

Once you receive your passport with a U.S. visa stamp in it, please check the visa stamp to ensure following:

• Name is spelled correctly, exactly as in passport.
  Given name in India is the first name in US. Surname in India is last name in US.
  Many times, in South India, the passport office puts the entire name in either the given name or the surname field. If your entire name is written in the given name or surname field, the U.S. visa office will put that entire name in the last name field in the visa and put FNU (First Name Unknown) in the first name field. And that's OK, there is no problem with that. However, in order to avoid this, if you have enough time, it is advisable to get this changed in the passport before applying for the US visa.
• Date of birth and gender (Male, Female) are correct.
• Date of issue and date of expiry are correct.
• Photograph is really yours.
• Visa type is correct: It should be B1/B2 for a visitor visa or business visa.
• Check whether the 'Entries' is 'S' or 'M'. 'S' means single entry and 'M' means multiple entry. If you have multiple entry, it means that you can enter the USA multiple times until the visa expires.
  Please note that even if you get a single entry visa, you can still go to Niagara Falls on the Canada side and come back to the USA. According to the visa officer on the Niagara border, single entry or multiple entry matters when you go outside North America and want to come back to the USA.

If any of the information is incorrect, please contact the US embassy or consulate or visa application center immediately to get it corrected.

There seems to be confusion regarding the validity of the visa stamp vs. duration of stay in the USA. Please note that the US visa stamp is used only to enter the United States. The duration you can stay in the USA is determined by the immigration officer at the port of entry, usually the airport. Even if you enter the United States on the last day of validity of the visa stamp, you may be granted 6 months stay. The duration of stay is determined by the date in the I-94 form at the time of entry into United States.

More details on visa stamp vs authorized duration.

If you get a 10 year multiple entry visa, you can come to the United States any time during those 10 years. There is no restriction to start your travel within a specified period such as 6 months of getting the initial visa.

A multiple entry visa also allows to you leave the U.S. one day and return right back to the U.S. on the next day. There is no specific period for which you have to stay out of the U.S. before you can enter the U.S. again. But if you try to enter the U.S. too many times, or try to spend most of your time in the U.S. by stringing visits together, the immigration officer at port of entry may suspect your true intentions and may deny your entry into the United States. While coming again to the United States the next time, you don't have to prepare any documents or send any affidavit of support again. You can just buy an air ticket, Visitor Medical Insurance and come to the U.S.

Once your travel dates are decided tentatively, you need to buy airline tickets. Usually 4 months return tickets cost less than 6 months return ticket. However, in a 6 months open ticket, you may be able to change your return date without any penalties.

You can buy an airline ticket either from India or from the USA. As tickets prices vary a lot, check out with multiple agents. Do not just buy the cheapest one available as it may have undesirable features such as longer stop over, longer route, more stops etc.

For buying tickets from the USA, you can check out the list of Travel Agents in USA. This list is provided just for your convenience and we do not represent or favor any agent in any manner.

Read Purchasing Air tickets page for detailed information about it.

When you buy tickets from India, some travel agents would want you to buy visitor medical insurance that they sell from Indian insurance companies. Some may even tell you that it is mandatory to buy this insurance before they can issue the tickets. It is NOT mandatory to buy visitor medical insurance just to get the tickets, but it is recommended to buy visitor medical insurance as medical treatment is very expensive and if you get any unexpected injury or illness, it is very advisable to buy visitor medical insurance from a company in the USA.

Visitor Medical Insurance from US Company.

You can compare multiple plans and make an instant purchase. Please read the FAQ to get answers to frequently asked questions. Sponsoring persons in the USA can also buy medical insurance for their visitors from this web site.

You are allowed to carry a certain amount of U.S. currency for use during your travel to the USA. Please check out Reserve Bank of India web site to get more details.

Generally, you should get most of your foreign currency in terms of travelers checks, available at many banks and money exchange bureaus such as American Express, Thomas Cook etc. Travelers checks are safer than cash. Please make sure that you keep the proof of purchase separate from the actual checks. Proof of purchase would be needed in case the checks are lost. As travelers' checks do not expire, you can use them during your next trip also in case they are left over. The most commonly used traveler's checks are American Express Traveler's Checks, Thomas Cook, Visa Traveler's Checks, Master Card Traveler's Checks.

You should generally get US currency of about $500 in different denominations of $1, $5, $10, $20 etc. Please note that banks/currency exchangers do not give you any coins. Unlike India, luggage trolleys in the USA are not free. Typically, the charge would be around $2. You would need cash if you would like to do some shopping at the duty free shops at the airport. You would also need some cash for snacks/incidental purchases at the intermediate airports like London, Frankfurt, Amsterdam etc. Shops at those airports accept US dollars so that you do not have to worry about currency in those countries.

• If you wear spectacles, you should note down the specification of your lenses in case you need to replace them in the US. You should also carry a couple of extra pair of spectacles with you as they are very expensive in the U.S. If you wear contact lenses instead, you should carry at least one extra pair with you. You should also carry necessary eye drops, ointments, lens cleaner solution etc. with you.
• If you are regularly taking some medicines, you should get the full stock of medicines, enough for the entire duration of your stay in the U.S. You can get common basic medicines without prescription and over the counter in pharmacies for common problems such as cough, cold, headache, mild fever etc. But if you require a prescription for the medicine, the pharmacy will not give it to you unless you have a prescription from a U.S. doctor. A prescription from a foreign doctor is not acceptable at the pharmacy. Also please note that if you are carrying any medicines that contain narcotic drugs or are addictive, you should get a doctor's certificate saying that it is medically necessary or else you may run into serious problems at customs.
• It is best to get a thorough check up of your body before traveling to the U.S., to avoid any surprise while on your visit. You can also ask the doctor about traveling precautions and make the list of all medicines and their compositions as you will not find the same brand of medicines in the USA.
• If you have problems while traveling such as nausea, dizziness, vomiting, ear pain etc, you should consult your doctor before traveling and get the appropriate medicines to take care of it.
• During take-off and landing, the cabin pressure changes which may cause ear blocking and ear pain. This may be relieved by chewing gum, or by opening your mouth widely as if you were yawning. Carry candies to chew and some cotton balls to stuff your ears, as they are not provided in most of the international flights.
• If you are diabetic or a gastric patient, you may request fruits in the airplane while traveling.
• If you are already having a cold, it will get worse while traveling. It is advisable to carry some nasal drops or other cold medicines. You should always consult your doctor first regarding this.

Applicants should be aware that a visa does not guarantee entry into the United States. Legally, the visa specifies the period during which the bearer may apply at a port of entry to enter the United States. The Customs and Border Protection (CBP) officer at the port of entry authorizes the traveler's admission to the United States and determines the period of authorized stay, not the consular officer. A person who receives a 10 year multiple entry visa has a 10 year period during which he or she may apply for admission to the U.S. It does not mean one can go to the U.S. and live there for 10 years. At the port of entry, an USCIS official may deny admission (which is equivalent of canceling the visa) to the holder of a valid visa if the traveler's activities will not be compatible with the specified visa category, or the USCIS officer discovers some fraud with the traveler. Legally there are various grounds of exclusion such as certain diseases, previously being out-of-status, criminal history based on which the USCIS officer can deny the entry into US despite the fact that the person has a valid visa. If a person contradicts a statement made at the Consulate, or if there is a discrepancy between the documents being submitted at the Port of Entry and the statements by the applicant, the immigration officer at a port of entry may return that person to his/her home country.

As it depends upon the immigration officer at the port of entry how much duration to give for stay in the U.S. For parents/in-laws coming to the U.S., it is advisable that you write a letter addressed to the immigration officer, explaining why they would require a 6 month stay in the U.S. and a sample itinerary for their travel plans would be useful too.
Samples:
Letter for port of entry for longer stay
Itinerary for longer stay

More details about Admission into United States

Please stay in the U.S. only till the date given on I-94 form. If you intend to stay longer than that, please apply for an Extension of Visitor Visa, well in advance, but not immediately after coming to the USA. If you overstay even for one day without extending your visa, it will automatically void the multiple entry visitors visa stamp in your passport. If you plan to visit the United States again in the future, you will have to apply for a new visa in your home country. It may also result in a 3 year or 10 year bar from entering the U.S., and if still in U.S., the person may also be removed from the U.S.

Also read,
Grounds of inadmissibility
Time bars entering United States