If you submitted an entry for the DV-2013 lottery (meaning you would have done so in the fall of 2011), tomorrow, May 1, 2012, is when you’ll be able to find out the results. They won’t be announced publicly: You will need to go to the State Department’s Electronic Diversity Visa website and enter your confirmation number, name, and year of birth.
If you win, congratulations — but realize that you are only at the beginning of the green card application process. You will need to submit various forms and documents, and prove that you are not inadmissible to the U.S. (for health, security, or financial reasons), and do so before the visas run out. (For more on inadmissibility, see Inadmissibility: When the U.S. Can Keep You Out.)
It might be worth your while to hire an experienced immigration attorney to help with this part of the process.