Planning to retire in 2024? Do this one thing now.

But when I asked a wide range of actual, practicing financial planners around the country for their retirement-planning ideas, I was struck by the responses. These are people who’ve helped scores, even hundreds (or perhaps thousands) of people retire over the years, from Portland, Maine, to Portland, Oregon, and from Miami to Maui. They’ve seen what’s worked and what hasn’t. And while they didn’t neglect the boring but important stuff, those weren’t the things they most wanted to talk about.

Their number one tip? Work out what you want to do when you are retired. Where you want to live. And how.

“Aside from the ‘Do I have enough money?’ financial question, there’s the psychological side,” says Brad Wright, a financial adviser at Launch Financial Planning in Andover, Mass. “Most people think about getting themselves to retirement, but few think about getting themselves through retirement. What’s your plan for the next 25-30 years?”

If you are on the threshold of retiring, he says, then you need to ask yourself key questions such as: “Where do I want to live? What do I want to do? Who do I want to do it with?”

If you plan to move, he also suggests giving the new area a trial run — or, at least, renting for a few months first before you think about buying. “I know more than a few people who have retired to Florida, only to return a couple of years later,” adds Wright.

“Before you retire, carefully consider what your next life steps will look like to add to your future happiness,” agrees Sandra Gilpatrick, a wealth adviser with her own firm in Boston. “Ponder what will give you joy and help you keep a connection to your community, contributing to a healthier life longer term.”

Marisa Bradbury, a financial planner at Sigma Investment Counselors in Lake Mary, Fla., is also in favor of making the most of your time. “Aside from the normal checklist items like budgets, healthcare, etc., I think it’s more important to review what you will do with your extra time,” she says. “Do you have hobbies and interests outside of work? Do you want to spend time volunteering? Traveling? And most importantly, do you have places to socialize outside of work — like church, a club, or family and friends? Make sure you have an idea of what to do with all your free time.”

Strategizing how to best spend your time is as important as figuring out the best way to spend your money. “Having the money to support your retirement isn’t much use if you don’t have a plan for how you’ll spend your time,” says David Foster, a financial planner with Gateway Wealth Management in St. Louis, Missouri. “People need a purpose to feel like their life has meaning. If work was your purpose for getting out of bed every day, and now that’s gone, with what are you going to replace that purpose?”

He adds: “There’s not necessarily a wrong answer to this question, but there needs to be an answer, or you’re liable to fall into a postretirement depression that can be hard to break out of.”

This, incidentally, is a bigger risk than many people may realize. Research shows that retirees are more likely to experience depression than those still in work.

“Having purpose in retirement is crucial for having a successful and enjoyable upcoming chapter of life,” agrees Rob Greenman, a financial planner at Vista Capital Partners in Portland, Oregon.

And try to go beyond the vague to the specific, advises Mitchell Kraus, a financial planner at Capital Intelligence Associates in Santa Monica, Calif. “Have you written down what your daily and weekly routine might look like in retirement? Have you had discussions with your family, friends and other loved ones about your retirement plans and dates? Who will be in your social network after you retire? What are your biggest fears about not having to go to work every day?”

Retirement may be longer than you realize. Men at 65 can expect to live another 17 years on average, says the Social Security Administration. Women at 65 can expect to live 20 years. And those are just the averages. At age 65 nearly 20% of men, and 30% of women, can expect to live into their 90s.

Catherine Valega, a financial planner at Green Bee Advisory in Winchester, Mass., says you should try to break this plan down into three phases: What you expect to do in your early “go-go years,” when you may be busy, traveling and doing things, your plans for the following “slow-go years,” when your energy, and maybe health, force you to take things easier, and the final (gulp) “no-go” years, which may well include time in assisted living or a nursing home, she says.

Once you’ve worked out why you are retiring, what you plan to do in retirement, where, and with whom—well, then comes time for all the boring but essential stuff.

Talking to a fee-only financial planner is never going to be a bad move. These things are ridiculously complex. The American tax, healthcare and benefits systems are an elaborate nightmare that make a mockery of the eighth amendment’s guarantee against “cruel and unusual punishment.” In this case, the punishment is usually crueler and more unusual the harder you’ve worked in your life, the more you’ve saved, and the more moving parts you need to track.

Will you be eligible for Medicare when you retire? If not, what are your plans to bridge the gap until you are? If so, which Medicare plan is the best for you, and what are you going to do about supplemental insurance? Do you have savings in pretax accounts, such as an IRA and a 401(k), and in posttax accounts including Roths? If so, have you worked out the best way to take money out to minimize your annual taxes? Do you have an estate plan? Are you better off owning your home (if that’s an option) or renting? Should you try to supplement your income with part-time work? Should you buy a lifetime annuity to ensure secure and stable income? And what is your plan if (or when) you become physically frail and need help? Can you afford long-term care? Do you need a long-term-care insurance policy?

Possibly the most important basic step is to draw up a budget—a spending plan.

Daniel Lash, a financial planner with VLP Financial Advisors in Vienna, Va., recommends a comprehensive, long-term one. 

“Have a detailed plan for different spending needs throughout the entirety of retirement which could span 20-30 years,” he advises. “This should include annual spending for basics and then spending for travel, house repairs, new cars, charitable giving, downsizing of house, long-term care,” and other expenses, he says.

Sandra Gilpatrick warns that getting the budget wrong early on can throw out the entire plan. “One of the common mistakes I see as clients retire is not planning enough in their budgets for the first few years in retirement,” she says. She’s seen people grossly overspend in the early years, “doing extra travel and fun activities.” If that coincides with a bad spell for their investments, that can have an outsize effect on the amount of money they’re likely to have left down the line.

This is just one reason many retirees choose to work part-time, often at something completely different, after pulling the plug on their main career. It can help provide a financial cushion, letting your savings last longer. But it’s also a chance to do something — lower paid, but interesting — you may have always wanted to do.

Laurie Allen, a financial planner at LA Wealth Management in Redondo Beach, Calif., recommends clients run a three-month trial run before actually retiring. During that time they try to live on their planned retirement budget. 

“For some, the amounts are the same, but for others their income will be somewhat less that they brought home while they were working,” she said. “I’ve had two people in the last years decide to delay their retirement, because the assumptions they made about how they would feel living off of less didn’t quite work out. They realized that it was worth it to go a few more years so that when they finally decided to call it quits, they had a more comfortable lifestyle.”