Renewing a Greencard is a fairly simple process in most cases. If your Greencard is about to expire or it has been lost or stolen you can get a new Greencard by filing form I-90 Application to Replace Permanent Resident Card with the U.S. Citizenship and Immigration Service. The form can be found here- http://www.uscis.gov/i-90 . It is important that you read the instructions carefully before filing and include the necessary supporting evidence and fee of $450. The process takes approximately 3 months. A few weeks after the initial filing, you will receive a receipt notice showing that your application and fee has been accepted and to wait for further notices. The next notice will be an appointment notice for biometrics (fingerprints). This will be scheduled about a month or two after the initial filing. After your biometrics are complete, unless there are any problems, your new card should arrive in the mail about a month later.
If you have ever been arrested or convicted of a crime or believe that you may have somehow violated the conditions of your lawful permanent resident status and need to replace or renew your Greencard DO NOT do so without first speaking with a qualified immigration attorney. If prior crimes or actions were in violation of your lawful permanent resident status then filing form I-90 or any form with USCIS could place you in removal proceedings. Seek out the aid of an immigration attorney who can best advise you on what your next steps should be.
If you received a conditional two year lawful resident card (Greencard) based on marriage to a U.S. Citizen and the two years is about to pass, DO NOT file form I-90. In this case you will not need to renew your Greencard; you need to file form I-751 Petition to Remove the Conditions of Residence. This form requires significant evidence of a bona fide marriage and must be filed within the 90 day period prior to the expiration of your conditional residency card. It is advised that you work with an attorney in filing this petition, especially if you have divorced your spouse or are contemplating a divorce.
If you are thinking about renewing your Greencard then it is likely that you have had your card for more than 5 years and may be eligible to apply for U.S. Citizenship. Consult with an immigration attorney to find out if you are eligible for U.S. Citizenship, as this may be a better option than continually renewing your Greencard.
Remember, in addition to obeying all U.S. laws, Lawful Permanent Residents must always have their Greencard, must always renew it when necessary and must advice USCIS of new addresses within 10 days of moving. Addresses can be changed by filing form AR-11 or online at http://www.uscis.gov/ar-11 .