What information is need in order to apply for a visa?

There are different categories of Visa for USA. Each category have different requirement. As if you want to obtain a work visa then first of all your employer will have to submit the immigrant visa petition to the related United States Citizenship and Immigration Service Center on behalf of the employee like nurse, carpenter etc.

I have read a detailed procedure for US Visa at some site that I have included in related links. It may gives you better understanding about the procedure.