It’s one of those tasks on many people’s to-do lists. But it’s way down at the bottom of the list: writing a living will.

A living will is a legal document, also called an advance health care directive, which details how you’d like to be cared for if something terrible unexpectedly happens to you and you wind up on life support. Do you want doctors to do everything they can to keep you alive, even if the outlook is hopeless? Or do you give them permission to let you go?

If you don’t have a living will, you’re in good company. According to a survey of 1,000 adults last year by the legal information site FindLaw.com, less than one of every three Americans have a living will. So if you’re among the two-thirds of Americans who likely don’t have a living will, here are some questions to consider — and some answers.

Do I really need a living will? It depends how you feel about the possibility of being in some sort of limbo where you’re alive but not cognizant. Obviously, if you feel strongly either way — you want to be sent on your way or you feel clinging to life support is still better than the alternative — you need a living will. Even if you have a “whatever happens, happens” mindset, you may still want to consider getting one. If not for you, for your loved ones.

[Read: 6 Decisions to Make Before You Die .]

“It’s important that your family and friends, when faced with having to make decisions as to your care, understand what your wishes and desires are regarding your end-of-life medical care treatment,” says Nancy Watkin, a Miami-based trusts and estates attorney at Berger Singerman.

It can get ugly and painful when these decisions are left up to the family. Nearly 10 years ago, St. Petersburg, Florida, resident Terri Schiavo was in the news almost every day. Her husband wanted her to go off life support; her parents didn’t. Her feeding tube was finally removed March 18, 2005; Schiavo died March 31.

How do I write a living will? You’ll fill out a form, which you can get from an estate attorney or a hospital. You can also download it online, but you’ll have to get it notarized, and attorneys and legal websites such as the U.S. Living Will Registry caution that living will forms on the Internet may be outdated. State laws change, so you’ll want to make sure the living will form you’re filling out is current.

Could you just write out your wishes or film yourself stating your wishes? Theoretically, you could, but you’re taking a chance. Jessica Dunne, an attorney at Chamblee, Ryan, Kershaw & Anderson P.C., in Dallas, doesn’t recommend it. “I always err highly on the side of caution,” she says. “I don’t think anything like that would be admissible in a court.”

Martin Shenkman, an estate attorney and certified public accountant in Paramus, New Jersey, agrees. “I’m all for being creative,” he says, “but hospitals have thousands of patients they’re caring for, and they have procedures. You don’t want to do something out of the ordinary.”

How much does it cost to put together a living will? More than you might think. “Living wills are typically executed as part of an estate planning package,” Watkin says. But if you only want a living will, she says, “an attorney would normally charge a nominal fee to prepare the document.”

[Read: 10 Steps to Writing a Will .]

If you really want to do this on the cheap, you could download a free form from a trusted source, or get it at your local hospital and have it notarized at your bank for $5 or $10.

But to make sure you get your living will right, you’ll spend more. A ballpark figure is $1,000 for an individual and $1,500 or $2,000 for a couple, according to Dunne.

And what would you get for spending more? “You really want four documents,” Shenkman says. “A will, a living will, a health care proxy and a power of attorney.”

The will, of course, is a legal document stating who gets what after you go. Odds are, if you don’t have a living will, you also don’t have a will. Earlier this year, the legal website Rocket Lawyer surveyed 2,048 U.S. adults age 18 and older and found that 64 percent of respondents didn’t have a will.

Maybe you don’t have a lot of assets or heirs, and you’re just concerned about what happens if you become incapacitated. In that case, along with the living will, the health care proxy and power of attorney are just as indispensable.

A health care proxy, also known as a durable medical power of attorney, is a document that appoints someone you know, often referred to as an “agent,” to make health care decisions if you aren’t able. While the living will indicates whether you want to remain on life support, there may be other decisions to make before physicians reach that point.

A power of attorney is a legal document that allows someone to make financial and legal decisions for you. As Dunne puts it, “Just because you’re in a car wreck and have a brain injury, that doesn’t mean you don’t still have rent and bills to pay and that 401(k).”

What if I want something between pulling the plug and keeping me around indefinitely? Depending on what the state’s advance health care directive form says, there may be room to write extra instructions. But if there isn’t, this is where an attorney can come in handy — in case the form needs to be modified in any way.

You can and should add your wishes, Shenkman says. For instance, he says, if your religion plays a role in why you want life-sustaining treatment, feel free to add that. If you want life-sustaining treatment for, say, a full week, just in case a medical miracle occurs, put that in there.

[See: 10 Money Questions to Ask Your Parents .]

“Topics you may wish to address in a living will include pain-management options, the use of prolonged life support, your preferences regarding resuscitation and your desires regarding organ donation,” says Anthony Criscuolo, a certified financial planner with Palisades Hudson Financial Group in Fort Lauderdale, Florida.

Where should I put my living will? You won’t do yourself much good if you lavish time, money, emotions and energy on your living will and then don’t tell anyone where to find it.

“A copy should be given to your physician so they’re part of your medical records,” Shenkman says, adding that the person you’ve assigned to make your health care decisions should also have a copy, and you should keep the original at home.

In short, you want everyone to remember it, so you can forget about living wills — and go on living.

More from U.S. News

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5 Questions to Ask Before Writing a Living Will originally appeared on usnews.com