Of course, we can only report about the visa we needed, about the L-1A visa (intracompany transferee).
The entire procedure begins with the signed offer, which the employer submits to the employee. This process is initiated by the employer in America by issuing various documents and submitted to the authorities. Then we have nothing to do yet.
After that, the employer sends us the documents and a confirmation document.
Our work began filling out the form DS-160.
This is a very long form; much information is requested, including passport, private address, marriage information. If you are already divorced, you should also provide evidence. A photo in a specific size is required, and a CV. The form obtained from the US counterpart has a significant number, which is necessary to fill out the form: the so-called receipt number.
It is actually a series of forms where you have the option to save the data between the steps, so you can change or continue it later. The website does not always work perfectly, so you really need a lot of patience. We often saved the data and updated the page.
If you do not go alone, you have to give you a lot of information about him/she, but you have to fill out the same form for the other person.
This request ends with a fee of $75 per person (in 2019). This is the application fee you have to pay, and it will not be refunded, even if you do not get the visa.
You have to pay an additional fee of $500 (in 2019) if your visa application gets approved.
The fee of $75 can be done online or by bank transfer. It is easier to pay online because you do not have to prove the success of the bank transfer (and it does not cost more).
An appointment can only be requested after successful payment of the fee. You could book an appointment immediately if you paid online.
We did not know that and waited for someone to contact us. When it finally turned out that we needed to book an appointment, we had to wait two weeks; that was the earliest available date.
The interview takes place in the US Embassy. You must bring with you the following documents/evidence: printed acknowledgment of the DS-160 form, the email with the confirmation of the appointment, proof of payment, a photo (there is a photo machine on-site).
We have taken additional documents, but in the end was not asked: Curriculum vitae, school papers, ownership about the property (the website has too much information, not necessarily straightforward, e.g., the medical certificate - but that is not required for an L-1A visa).