The U.S. Department of State gives a run-down of employment-based immigration visas. You will want to look into these if you intend on working in the country. They are necessary if you intend to stay more than several months.
You can divide work visas into three categories. They are:
Outstanding researchers and professionals
People with extraordinary ability and
Multinational executives or managers
Outstanding researchers and professionals must be internationally recognized. They should have at least three years of experience with research or teaching. Persons with extraordinary abilities can apply to any number of fields. It can include business, arts, sciences, education or athletics.
For example, a traveling pop star would fall under this category. So would a famous athlete. Multinational executives or managers must have one to three years of employment under their belt. They must have worked as a manager or executive, and the position they apply for must be the same.