(CNN) -- It's a situation no one wants to be in: staring at the serene face of a loved one as doctors discuss ventilators, feeding tubes and EEG results, wondering whether this is what your mom or brother or spouse really would have wanted.
The heartbreaking story of 13-year-old Jahi McMath has made many question what they would do in a similar situation.
Doctors declared Jahi brain-dead after a tonsillectomy in early December. A judge agreed, but the family battled to keep Jahi on a ventilator. The eighth-grader has since been released from the hospital and moved to an undisclosed location, where the family's attorney says she is "improving."
If you were Jahi, is that what you would want? Does your family know the answer to that question?
In one California study (PDF), 84% of the people surveyed said their loved ones had a good idea of or knew their wishes exactly, yet only 29% had ever had a serious, in-depth conversation about end-of-life care.
"It's awkward," said Paul Malley, president of Aging with Dignity. "People think, 'I don't need to do that today.' There's that assumption that you only need to talk about end-of-life care if you're old and sick. These cases that have played out in the news show it's just the opposite."
Here are five things you need to do now:
Find someone to speak for you
The first thing you need to do is identify a health care agent, also called a proxy or surrogate. This is the person who will speak for you and make decisions about your health when you are no longer able to communicate.
This person should be someone you trust, who will understand and agree to your wishes. They should also, Malley says, be someone with a strong backbone who won't be afraid to fight for you. And oftentimes, "it's not the first person who comes to mind."
For instance, your spouse may not want the responsibility of removing life support after an accident. Or your sibling may disagree with your wish to return home if doctors say further treatment will only prolong the inevitable.
"Anytime we're caring for a loved one, there is emotion involved," Malley said. "Sometimes it's helpful to have a person who's a little bit removed."
Determine what you want -- and what you don't
If your heart stops, do you want medical providers to perform CPR? If you cannot breathe on your own, do you want to be intubated? If you cannot eat or drink, do you want to be fed and hydrated artificially?
Would you want treatment if you can no longer respond to commands? Would you tolerate severe pain or nausea if the chance of recovery was 80%? How about 20%? Do you want to donate your organs when you die?
Use this toolkit from the American Bar Association (PDF) to help guide your wishes. Know that it's not possible to address every situation, and many experts warn against making your mandates too broad.
Write it down
Talking with your health care agent about your wishes is important, but it's also a good idea to put them in writing. That "takes the guessing game away" in the case of disagreements about your care, Malley says. "Ultimately, that written record becomes a gift to family and loved ones."
The document in which you identify your health care agent is called a Durable Power of Attorney for Health Care, according to the American Bar Association.
This is slightly different from a living will, which states only your wishes about life-sustaining medical treatment if you are terminally ill, permanently unconscious or in the end-stage of a fatal illness, the bar association's website says (PDF). The Durable Power of Attorney for Health Care covers everything. Both documents are called advance directives.
Print out your advance directive and make copies for your health care agent, family and spouse. Ask your primary care physician to place a copy in your medical file. Keep the original someplace safe but accessible. "The last place you want to put it is in a safe deposit box," Malley said.
You can also store the file online at LivingWillRegistry.com. The site will give you a wallet card with a registration number that medical providers can use to access it.
Know your state's laws
In Texas, 33-year-old Marlise Munoz's body is being maintained by technology after she was declared brain-dead. Erick Munoz says his wife didn't want to be kept alive by a machine, but the hospital won't turn it off. Munoz is 19 weeks pregnant, and Texas law prohibits withdrawing "life-sustaining treatment" from a pregnant patient. Thirty states have similar end-of-life laws regarding pregnancy, according to a 2012 report (PDF).
Munoz's story illustrates the importance of knowing your state's specific laws regarding advance directives.
While most states require only your signature, the date and two witnesses on an advance directive, four require legal notarization. Eight states have specific forms you need to use. In Ohio, there is a mandatory statement that has to be written in all capital letters and attached to the advance directive to make it legal.
If you don't select a health care agent, most states have a pecking order: spouse, adult children, parent, sibling, etc. But in Wisconsin, there no next of kin authority -- meaning if you don't name a health care agent, no one would be able to step in and make decisions for you. In West Virginia, the patient's attending physician can select who will be the best decision-maker in that situation.
In some states, getting married revokes the power of your health care agent, be it a parent, sibling or friend; your husband or wife automatically becomes your health care agent unless you do another advance directive.
These are just examples. To familiarize yourself with your state's laws and the laws in the state where your family lives, visit Caringinfo.org.
Think about more than the medicine
When Alexandra Drane's sister-in-law was near death, Drane's husband insisted that they bring the young woman home, despite several other family members' protests. Rosaria Vandenberg had a brain tumor that was slowly taking away her ability to function. The night before Vandenberg died, her 2-year-old daughter crawled into bed next to her. Vandenberg had been unconscious for a week, but right then she opened her eyes and stared into her baby girl's face with pleasure.
"If the family had not found the strength to take her home, would Za have ever held her daughter again?" Drane wonders on her advocacy site, EngageWithGrace.org, which encourages people to talk about end-of-life care.
Sometimes the little things make a big difference when you're ill. For Malley's grandmother, it was having her toes free; she hated when the hospital nurses tucked the blanket under her feet, he says.
Let your health care agent know if you have specific spiritual requests or would like music piped into your hospital room. Aging with Dignity offers "5 Wishes," a downloadable advance directive that's legal in 42 states and addresses these types of non-medical end-of-life issues.
"People say, 'I want to be with my family. I want to be comfortable. I want to be home if that's possible,' " Malley said. "What are you most concerned about? What are your fears? Oftentimes, people near the end of life are afraid of being alone, afraid of being in pain, and they're afraid of losing control."