Of course, thinking about these issues is not fun, which is probably why most people avoid it. You have to ponder some of the grimmest circumstances imaginable. Do I want to be on a respirator if I'm conscious? If I'm unconscious? Do I want food and water withheld? How about pain medication?

There are so many issues to ponder that I highly recommend ordering copies of Your Way, a guide created by nonprofit group HELP, to aid you in deciding what you want and don't want if you're incapacitated.

Decisions about health care and money

You also have to figure out whom to name as your "attorney in fact," or proxy, to help implement these decisions for you. Keep in mind:

  • Two heads may be better than one. You don't have to name the same person for both powers of attorney. In fact, many people find that the people they trust to make health care decisions are different from the ones they want handling their finances.
  • Spouses are good, but have a backup. If you're married or in a committed partnership, that person is a logical choice to fill both roles. But you'll still need backups in case he or she is injured or killed in an accident with you, or is unable or unwilling to serve.
  • Keep them close. For the health care directive, you'll probably want people who are nearby or at least willing to travel to the hospital to be with you, perhaps for an extended time. The person handling your finances may be able to do so remotely, although you may still prefer to name someone who lives relatively close for convenience. In addition to paying your bills and handling insurance claims, the person handling your finances may also need to sell your home or make other complicated moves that require more proximity.
  • Make sure they're tough. With your health care proxy, especially, you need someone who's forceful enough and committed enough to your stated wishes to advocate for you, regardless of what others (including family and medical professionals) might think.

You can change these documents at any time, as long as you're still competent. You probably should review them about once a year to make sure you're still comfortable with your decisions.

My father gave his wife his power of attorney for both finances and health care in his estate documents, but unfortunately, no backup people were identified. Frail and elderly, his wife was overwhelmed by the situation and the need to take over functions, from balancing the checkbook to making travel arrangements, that had always been his. After two months, her own ill health caused her to return to her native Australia.

Had my dad lasted much longer, we might have had to go through an expensive court process to identify a new guardian to make decisions for him. As it was, his wife finally made the choice to put him on palliative care, which managed his pain without continuing medical intervention to try to keep him alive. He died several days later.

My dad was quite fortunate in one sense: He had plenty of people who loved him. I've heard from other older folks who couldn't think of anyone they trusted enough to give their power of attorney. If that's the case for you or any older person you know, a family attorney or certified public accountant might serve, or a professional trustee might be an option. All major banks and trust companies have these professionals.

Once you make these arrangements for yourself, start bugging your parents to get their documents in order. If you're not sure how to start that conversation, you can tell them about your own efforts to deal with incapacity or relate a horror story from a friend's experience (ask around; you'll find some). If nothing else, just email them this column with a "let's talk about this" note.

Parents of minor children: This one's for you

Now, back to the issue of wills. I was being a bit facetious above, since many people want more control over who gets their stuff than state law dictates. If you're wealthy, estate-planning documents also can help you reduce potential taxes, which can give you peace of mind while you're alive.

That said, there is one group of people who should absolutely, no question, have wills, and that's parents of minor children. Even if you can't agree on who gets the crystal, you need to agree on who would take care of your children in the event of your death. No matter how icky you feel about planning for your own demise, you owe it to your kids to spare them the potentially ugly and drawn-out custody battle that could ensue if you don't make these decisions now.

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So go make that appointment with an attorney or buy the software -- right now. A small investment of your time could spare you and your loved ones a lot of grief.

Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.