U.S. Citizenship and Immigration Services recommends filing Form I-90, Application to Replace Permanent Residence Card, six months before the initial green card expires. If your card has already expired, you are still eligible to fill out the form.
If you are outside the United States, but plan on returning before your green card expires, U.S. Citizenship and Immigration Services suggests that you wait until your return to file a I-90 form. On the other hand, if you are outside the United States and your green card is already expired, contact a U.S. Consulate, USCIS office or any U.S. port of entry before attempting to file a I-90.
Application status can be checked on the U.S. Citizenship and Immigration Services website under the category "My Case Status." If for whatever reason the application is denied, you are notified by mail and the reasons for denial are detailed in writing. Although individuals are not allowed to appeal a negative decision, the opportunity exists to reopen or question the findings of the office which denied the claim. These concerns can be taken up with the Administrative Appeals Office, or the Board of Immigration appeals through the Department of Justice, according to U.S. Citizenship and Immigration Services.