As a U.S. citizen of at least 21 years of age, you are eligible to petition your parents to acquire lawful permanent residence in the United States. However, if you are a lawful permanent resident or green card holder, you are not eligible to petition your parents for U.S. permanent residence. As an eligible petitioner, you are also required to submit evidence of your income and/or assets to prove that you are capable of supporting your parents once they arrive in the country.
Start the petition for your parents by filing Form I-130, Petition for Alien Relative, which establishes your relationship with the relatives in question. In some cases, the Form I-130 can be submitted for processing together with Form I-485, Application to Register Permanent Residence or Adjust Status, if your parents are already in the United States and just need to apply for a status adjustment.
Submit Form I-864, Affidavit of Support, to prove that you are capable of supporting your relatives when they immigrate to the United States. Most immigrant categories require you to file an affidavit of support for the purpose of providing evidence that the relatives under petition have the financial means to live in the United States and will not require welfare or financial support from the U.S. government. Other relatives in the U.S. may also help you sponsor them, if you do not meet the financial qualifications.
There is no waiting list for parents under immigrant visa petition. Special consideration is provided by law to immigrate immediate relatives of U.S. citizens, including parents. According to Immigration Direct, "The U.S. Department of State will invite them to apply for an immigrant visa as soon as USCIS approves your I-130 petition."