The Tipping Point: When Should You Write Your First Will?

Maria Cornelius decided to write her first will after being diagnosed with breast cancer in 2012 at age 50. "I realized anything could happen on the operating table ... and anything could happen with the diagnosis," says Cornelius, a writer and editor at Moxley Carmichael, a communications firm in Knoxville, Tennessee.

To draft up the required legal documents, Cornelius got in touch with a friend who is an attorney. "She understood the urgency and immediately got the paperwork," Cornelius says. "We were finalizing everything the week before I had surgery, everything was getting signed and notarized."

With her friend's help, Cornelius identified an executor, determined what to do with her valuable assets, such as bank accounts, antique furniture and sports collectibles, and detailed funeral arrangements. Cornelius, who is unmarried and doesn't have kids, was able to identify how her belongings would be split among her beneficiaries, including her niece, nephews and siblings.

The diagnosis was a wake-up call to get her affairs in order, says Cornelius, who has been cancer-free for four years. "I'm the classic case of waiting until something forces you," she says.

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

Cornelius is not alone in waiting to experience a life shakeup before considering life after her death. The motivation for writing your first will -- and getting other estate-planning documents in order -- usually stems from major life events. "There is usually something that triggers it," says Stuart Bronstein, an attorney in San Francisco, who hosts public will-writing workshops at local libraries.

Here are a few common tipping points when it comes to writing a will. But word to the wise: Don't wait until after a traumatic -- or happy -- event reminds you of your own mortality. If you don't have a plan in place, consider making one now.

Becoming a parent. "The birth of a child is the biggest tipping point for most people to write their first will, but it's also the most difficult time," says Melissa Sotudeh, a wealth advisor at Halpern Financial in Rockville, Maryland. "People get really stuck on who will be the custodial guardian of their children -- the person who would take care of their children if the parents were gone."

Parents should also determine the financial custodian, Sotudeh says. She often sees parents give the guardian and financial custodianship duties to different people to include some checks and balances.

For Bob Bissen, 56, leaving his two children at home while he embarked on an adventurous vacation with his wife was enough to kick off his desire to write a will. "We had always told ourselves that we needed to write one, but had always come up with an excuse -- time, cost or need -- to put it off," says Bissen, who lives in Fairfax County, Virginia, in an email.

Before Bissen and his spouse headed off on a heli-hiking vacation, during which they took helicopter rides to far-flung hiking sites, in British Columbia, they created their first will. To save money, Bissen says, they used LegalZoom.com, a site that provides legal help and resources, and had the documents witnessed and notarized. "It provided us some much-needed reassurance as we left for the airport," says Bissen, who works as a government-relations consultant.

[Read: 5 Estate Planning Strategies to Keep Your Money in the Family.]

Watching a loved one pass away. For others, seeing a relative or peer pass away reminds them of their own mortality and sparks the desire to create a will and get other legal documents in order. "People see something that happened to somebody else -- a parent died, a friend died -- and they see that either things run smoothly because they have a good estate plan, or they don't run smoothly because people don't," Bronstein says. "They say, 'I've got to do something.'"

If you already have a will in place, seeing a friend or relative die may also be a wake-up call to make sure that parents and siblings have their own estate-planning documents established. Bronstein says he often sees people bring parents into his will-writing workshops.

[See: 10 Retirement Planning Moves to Make in Your 20s.]

Getting married. Combining assets with a spouse or partner might trigger the creation of a first will, even if you don't have children. "It's around the time that either you're thinking of getting married or sharing assets with somebody else, and there starts to be a need to have clarity on what will happen [to] those assets when you pass away," says Jamie Ebersole, a certified financial planner in Wellesley Hills, Massachusetts.