There are many types of wills and trusts; determining which is best for you and your pet depends on your situation and needs. It's important to seek the advice of an attorney who both understands your desire to provide for your pet and can help you create a will and/or trust that best provides for him.
You and your attorney also need to make sure that a trust for the benefit of one or more specific animals is valid and enforceable in your state. Even if your state law recognizes the validity of such trusts, keep in mind that tying up a substantial amount of money or property in a trust for an animal's benefit may prove to be controversial from the point of view of a relative or other heir. Moreover, trusts are legal entities that are relatively expensive to administer and maintain, all of which underscores the need for careful planning and legal advice.
After you and your lawyer create a will, a trust, or both, leave copies with the person you've chosen to be executor of your estate as well as with the pet's designated caregiver so that he or she can look after your pet immediately. (The executor and caregiver may or may not be the same person.) Make sure the caregiver also has copies of your pet's veterinary records and information about her behavior traits and dietary preferences.