Preparing an advance directive involves more than simply filling out a form. The time you spend thinking about the kind of care you want, or don't want, and discussing your wishes with your family and loved ones is much more meaningful than simply checking off boxes on a form. The written document is a good way to memorialize and record your thoughts and choices, but it is no substitute for time spent discussing those choices with your loved ones.
You might want to start out by visiting the American Bar Association's web site to learn the basics about advance directives. Then visit "On Our Own Terms" and read page 14 of the Discussion Guide. This will help focus your thoughts on what decisions you need to make now so that your choices will be followed when the need arises.
When you are ready to prepare your document, remember that each state has its own law, and sometimes, its own form. While it is usually not necessary to have an attorney help you prepare an advance directive, you may want to consult an attorney if the various forms you obtain do not fit your needs or if you have any special concerns. After you have prepared your advance directive, consider registering it with the U.S. Living Will Registry so that your choices will be available to health care providers and your family wherever and whenever needed.