Your first step would be to contact your Funeral Director. Laws vary from state to state (some do not allow pets to be interred in human cemeteries, some do and some have no laws regarding it at all) and locally. Your Funeral Director will be able to guide you regarding the state and local laws, and then you will need to find an appropriate cemetery.
Some cemeteries also have prohibitions on pet burial, so make sure to check with your cemetery of choice. The best idea is to go ahead and do your research and homework and plan ahead for future burial plans.
Make sure your plans and the documentation are in an easily accessible location so that your next of kin know your wishes to have your pet buried with you.