Every year the US Government announces the Eligible Countries for the participation in the Green Card Lottery.
Eligible countries are the ones that have not received over 50,000 Green Cards in the last 5 consecutive years. The eligibility list changes every year, which is why participants should always pay attention to these changes.
The eligibility is based on two main factors.
You can claim your eligibility based on the country where you were born.
However, if your country does not qualify for the lottery but you are legally married to a citizen from an eligible country, you may claim eligibility based on the country of birth of your spouse. Furthermore, if you were born in an ineligible country but your parents weren't, then you may claim their country as your Eligibility Country.
You can claim eligibility based on your education or work.
You can claim eligibility based on your Education if you have successfully graduated 12 years of primary and secondary school, equal to the American 12-year high school system. You should also be able to provide a certificate, confirming your educational history, during the interview, in case of winning the lottery.
If you wish to claim eligibility based on your Work Experience, you should have worked for at least 2 years in the last 5 consecutive years. Your work experience must require at least 2 years of training in the respected field. To verify you meet the work requirements of the US Government, please check the Department of Labor's O*Net database.