There are several ways to get permanent residence (green card) in the United States. The most common are employment-based, having a particular skill set or family-based.

Employment-based permanent residence
Is based on a job offer from a U.S. employer or high achievement in a specific area. The five categories of employment-based permanent residence include: priority workers, professionals with advanced degrees, professionals and skilled workers, religious workers and investors. (more information on employment-based permanent residence)

First Preference (Priority workers)
Extraordinary Ability (more on the EB-1(1) )
Outstanding Researchers and Professors (more on the EB-1(2))
International Executive and Managers (more on the EB-1(3) )

Second Preference (Advanced degree and exceptional ability)
Advanced degree professionals (EB-2(1))
Exceptional Ability (EB-2(2))

Third Preference (Professionals and skilled workers)
Skilled Workers (EB-3(1))
Professionals holding a bachelor's degree (EB-3(2))

Fourth Preference (Religious Workers)
Religious Workers (more on the EB-4)

Fifth Preference (Investors)
Employment creation investors (more on the EB-5)

Family-based permanent residence
Is based on a family relationship to a U.S. citizen or permanent resident. (more information on the family-based permanent residence)

Immediate Relatives
Immediate relatives that qualify are spouse, parents and minor children of U.S. citizens.

Preference System
Preference system relatives are adult children and siblings of U.S. citizens; and spouses and minor children of permanent residents.