Pet adoption requirements vary from shelter to shelter. You can usually find this information on the FAQ page on your shelter's website. Most shelters have age requirements and adoption fees, but some may also impose additional restrictions and requirements.
There are no universal requirements for pet adoption since each adoption center creates and enforces their own set of requirements. However, most adoption centers have relatively similar requirements. The Humane Society requires that an individual be at least 18 years of age with a valid ID to adopt a pet. They also require that all dogs be spayed or neutered and implanted with a microchip as a form of permanent identification before leaving the shelter.
The Society for the Prevention of Cruelty to Animals, or SPCA, requires individuals to be 21 or older and have the proper facilities to maintain and contain the pet before the shelter will release it for adoption. Similarly, PetSmart requires an adoption interview, paperwork and an adoption fee before releasing the pet.
For the most accurate and relevant information, always check with your shelter of choice to find out what their specific adoption requirements are. This information is usually available online or you can stop into your shelter for more detailed information and an opportunity to meet the pets that they have currently available for adoption.