This might be an obvious tip for any would be immigrant, but it may still be useful to refer to. Every year a few of the green card applicants are chosen to get a permanent residence in USA. There are various companies selling green card application service for rather hefty prices (such as USFIS, USGIS etc.) by trying to simplify the process. However, officially, applying is completely free and all the information is on the USCIS (US Citizenship and Immigration Services) site: http://www.uscis.gov/greencard

Applying for a green card lottery (also known as "diversity lottery") isn't exactly a sure way of getting it, could take years of re-applying, and so probably isn't the only thing to rely on if you're intent on moving, but it may be worth trying, just in case.

If you decide to apply for a green card lottery, good luck!