Contact your state's Department of Environmental Conservation. They can send you study material. In New York, the test is given once a year in a specified location. It's a timed test, so the best way to prepare is to make flashcards so that you can study. If you pass, you can then let the DEC know what kinds of animals you would accept (ex. juveniles, waterfowl, large mammals, etc.) To work with raptors or vector (possible rabies carrying species), you would need additional training. Once you're certified, you can elect to have your name posted in a book that is sent out to other rehabbers. You renew your license for free at the end of each year and send in your tally sheet with a list of animals that you rehabbed and other info. This is a great way to work with animals but you need to find a vet who will work with you if you need advice or medicines. Some vets refuse to help you even if you are helping a wild animal. Many people think that you are paid and don't realize that you will be spending a lot of time and money yourself with compensation. A good rehab success rate is 50% with most of the injured animals that you see having been attacked by pet dogs and cats.