For those outside the U.S. to apply for a work visa (Generally an H visa), the prospective employer in the US, not you, must first file a work visa petition and obtain approval from USCIS before you, the foreign worker, can apply for the work visa at a U.S. Embassy or Consulate. Your first step is to find an authorized employer willing to sponsor you – beware there are lots of fraudulent employment schemes. I do not get involved in the employment part of it, you are on your own. Approval of the employer's petition does not guarantee you will be issued the H visa. You can still be turned down even if you have an approved petition. All reputable and established employers know the process, and would not just issue an offer to a foreign national residing outside the U.S.
LIMITATIONS & REQUIREMENTS
Please note: You cannot legally work on a B visa, nor are you eligible to apply for a work permit. For those in a profession requiring U.S. licensure to practice their profession (nurses, engineers, physicians, lawyers, dentists, architects, teachers, public accounting), you are required to satisfy all requirements and must have the required license in order to be granted the visa by the embassy. Working or attempting to find employment while in the U.S. on a tourist visa (B1/B2) visa is a violation of law and is grounds for cancellation, revocation, and deportation. If you have been turned down for a work visa, you are unlikely to get a tourist visa. Specific immigration advice, explanation, and procedures are only provided, in telephone or office consultations.