
There are many different scenarios under which an individual could qualify for a green card. In general, the most common involve either being sponsored by a family member or being sponsored for employment by a U.S. company.
You can find general information on the most common categories at:
http://travel.state.gov/visa/bulletin/bulletin_5640.html
In general, you may want to look at non-immigrant options for the U.S. before looking at any permanent options.
Regards,
Andrew M. Wilson, Esq.
Serotte Reich Wilson, LLP