It really depends on your situation. If you have a new evidence that was not available at the time you submitted your application, you may file a motion to reconsider. If you think the USCIS should have approved your petition, then you can appeal.
Elkhalil Law Firm, LLC
Disclaimer: This answer is for informational and educational use only. This answer does not create attorney-client relationship. For more details, I recommend a private consultation with an immigration lawyer.