Sometimes people just sign documents without even reading them. This practice is a dangerous one, especially when it comes to a power of attorney.
Be wary of general power of attorney document that gives broad power and has no expiration date. I have seen two situations with horrific outcomes: 1), where a person did not even realize he or she was signing a power of attorney document, as it was done by trickery, and 2), where a person just did not thoughtfully choose the proper person to which to give the power of attorney. In both situations, the people were stripped of their assets by others they thought they could trust. Both situations could have been prevented.
First and foremost, read everything you sign. Do not trust anyone, even loved ones and family members when they put something in front of you and tell you they just need your signature. When money is involved, unfortunately people can become selfish. People can become quite nasty and unrecognizable when it comes to something they think they are owed.
Second, when you need to assign a power of attorney for a specific purpose, limit the document both in scope and time. Some examples may include for the purpose of taking care of certain finances while away on an extended trip or to make health care decisions during a hospital stay. Consult an experienced attorney to draft this power of attorney document for you and your best interests. It is ill advised to have the person in which you are giving the power of attorney draft the document. Finally, sign the document in the presence of witnesses and have it notarized.