Hard to believe that there could be a document more important than a will, but there is one.  Its called a Power of Attorney and it gives someone the legal authority to handle certain matters in the event a person does not want to handle them on their own.  Let's say that an elderly father is having difficulty managing and keeping up with his monthly expenses.  He might "give" a Power of Attorney to his daughter to write checks out of his account and pay his bills.  In this example, the father is the "principal" and the daughter is the "agent" or "attorney-in-fact".  The authority provided under a Power of Attorney can be fairly limited, as in the example above, or fairly significant, such as providing someone with the authority to make gifts, negotiate securities and real estate, or transfer funds. 

You might have also heard the term "Durable Power of Attorney".  A regular Power of Attorney is used when the principal is still competent and is usually given out of convenience.  The power provided under a regular Power of Attorney is revoked should the senior become incapacitated.  To prepare for the possibility in the future that the principal may not be competent due to disability, incapacity, or the normal aging process, they should provide someone now with a Durable Power of Attorney.  This document provides an attorney-in-fact the ability to manage some or all of their affairs should the principal become incapacitated or incompetent and remains effective until they pass away.
 
As an adult child and caregiver, it will be important to ensure that your parent has a Durable Power of Attorney.  In the absence of one, a court would appoint a guardian to manage the incompetent person's affairs.  This process can be expensive, time consuming, and to some it can be humiliating.  So, as is the case with other legal documents I’ve discussed, plan for the future now so you and your parent have the peace of mind that all of their affairs will be taken care of in their best interest and consistent with their wishes.  You should consult with an eldercare lawyer to be sure that all state-specific legal requirements are met (for example, it may be necessary to have more than one durable power of attorney if your parent has assets in a number of states).   At a minimum, Powers of Attorney documents name the person granting the authority, the attorney-in-fact, an alternative attorney-in-fact, the list of powers to be granted, the terms and circumstances of the power granted, and the signatures and seals as required by each state.  Most major financial institutions have their own forms for power over certain accounts, so be sure to coordinate your efforts with any banks or brokerage firms.