The choice of winners of the U.S. diversity visa lottery is completely random. For the 50,000 available visas each year, between 13 million to 20 million eligible people from various countries in the world apply. (I.N.A. Section 203(c).)
Of course, people are always looking for ways to increase their chances of success. For example, some have tried entering more than once. This led the U.S. Department of State to implement a system that automatically disqualifies anyone who submits multiple entries. (And the disqualification applies to ALL your applications.)
You can, however, increase your family's chances of becoming residents of the United States by various legal and acceptable means, which we'll discuss in this article.
The best way to increase your family's chances of success is to have all eligible family members register for the lottery. For details on who meets the country, educational, and other eligibility requirements, see Winning a Green Card Through the Visa Lottery. A winning applicant can bring both spouse and unmarried children under age 21.
For example, let's say you and your spouse are both citizens of New Zealand, you both work in skilled jobs, and both graduated from secondary school. As a family, you now have two numbers that might win the lottery. You can file one application under your name, and your spouse can file one application under his or her name. You will each receive a confirmation number. If one of you wins, the other enters as a derivative spouse.
It is important to remember that each person applying for a diversity visa must meet the eligibility requirements. Therefore, if your spouse does not meet the employment, country, or education requirements, he or she is not eligible to apply on his or her own.
There is no limit on how many eligible members of the same family may apply. If you have any children who have met the educational or work experience requirements (which usually requires them to be at least 16 to 18 years of age), those children should also enter the lottery. They won't, if they win, be able to bring you to the U.S. immediately; but they will start a path to helping you and other family members immigrate in the future.
For example: You and your 20-year-old son are eligible for diversity visas, and you both apply. Your son wins, but you do not. Your son enters the United States and becomes a lawful permanent resident. After five years of living in the U.S., your son can become a U.S. citizen. As a U.S. citizen, he can petition for you (considered his "immediate relative") to become a resident of the United States.
For more information on family based immigration, read the article Green Card Qualification.