Well it depends on you situation.. Where you currently reside and your educational / family background.For example you can be a student, apply to university in the States, apply for a job, apply for a work permit (H1-B) VISA and maybe your employer can sponsor you for a green card. Other possibilities include getting sponsored by a family member who already has a green card, or through politicaly asylum (if you are a refugee of your country for example), or if you marry a U.S. citizen. I can't go into much more detail not knowing your particular situation but a great site is
http://www.soyouwanna.com/site/syws/...ncardFULL.html and has information for various ways for obtaining the green card.
www.soyouwanna.com