To obtain a US visa, you must follow several steps:

1. Decide your visa type: The visa can be tourist, student, work, etc. Select the visa type that suits your purpose of travel.

2. Fill out the DS-160 form: This is an electronic form that you fill out online on the website of the US Embassy or Consulate in your country.

3. Register on the CEAC website: This is necessary to pay the consular fee.

4. Pay the application fee: After completing the DS-160 application, you will be required to pay a fee, which depends on the type of visa.

5. Schedule an Interview: After paying the fee, you will be able to schedule an interview at the U.S. Embassy or Consulate. Typically, interviews are scheduled through an online scheduling system.

6. Gather the necessary documents: You will need a passport, photographs, proof of financial solvency, letter of invitation (if any) and other documents depending on the type of visa.

7. Complete the interview: On the day of the interview, report to the US Embassy or Consulate with the required documents. Be prepared to answer questions about the purpose of your trip, plans in the USA, financial status, etc.

8. Wait for the decision: After the interview, you will be notified of the decision to issue or refuse a visa.

If your visa is approved, you will receive it in your passport. If there is a refusal, you will be provided with an explanation of the reasons for the refusal.

There are several reasons why people may be denied a US visa:

1. Unsatisfactory evidence of ties to your home country: One of the main criteria for issuing a visa is to convince the consul that you have strong ties to your home country and do not intend to remain in the United States illegally. If the consul doubts your ties to your homeland (for example, lack of a stable job, family, property, etc.), this may be a reason for refusal.

2. Insufficient Financial Support: Consuls may deny a visa if they believe that you do not have sufficient financial means to cover expenses during your stay in the United States.

3. Unconvincing purpose of travel: If your purpose of travel or plans in the US do not seem convincing, or if the consulate believes that you have hidden intentions, this may also lead to denial.

4. Unsatisfactory Documents: If your documents are completed incorrectly or incompletely, this may result in a denial.

5. History of visa violations: If you have had problems with US visas in the past (for example, illegal stay, violation of the terms of stay, etc.), this may affect the consul's decision.

6. Interview failures: Your behavior or answers to questions during the interview can also affect the consul's decision.

It is important to prepare for the interview by providing all the necessary documents, clearly explaining the purpose of your trip and convincing the consul of your ties to your homeland and financial viability.

Seeking help from specialists such as immigration lawyers (for example link) or visa agencies can be helpful in a number of situations :

1. Complex Cases: If you have complex circumstances or problems with previous visas, professional help can help you understand your rights and the best strategies to resolve the problem.

2. Document preparation and interviews: Specialists can help you prepare all the necessary documents and prepare for the interview, which will increase your chances of successfully obtaining a visa.

3. Support during the process: Immigration lawyers and agencies can provide you with the support and guidance you need throughout the visa process.

4. Resolving complex issues: If you have any specific questions or concerns about your rights or visa options, professionals can help you understand the situation and offer solutions.

It is worth remembering, however, that specialist services may cost additional money, so before seeking help, you should weigh the pros and cons and decide whether it suits your needs and capabilities.