If you are looking for the easiest way to immigrate to the United States you should be looking for work in the United States. The easiest way is to get a green card through the sponsorship of an employer. When using this method you may have to wait a few years to get a permanent citizenship card but you will be able to legally stay and work in the United States in the meantime.
Another way that people often immigrate is through marriage. A person can get a green card when legally marrying someone that is already a citizen of the United States. It is also possible to be able to get a green card if your parents are citizens already as well.