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If you are one of the nearly half of Americans who can't afford to retire, here's good news. Even if you're approaching retirement with little or no savings, retirement experts say there's much you still can do to construct a satisfying, if modest, retirement.

But you'll need to act soon and avoid the paralysis that can come from fear and resistance to change. Your reward: a more-comfortable life in years to come.

Americans of all ages are facing a dire retirement savings shortfall, says retirement-security expert Teresa Ghilarducci at the New School of Social Research in New York. She predicts that slightly more than half of middle-income and lower-income Americans will be living at or near the poverty line in old age.

Ghilarducci and colleagues extensively analyzed all the research on retirement readiness and savings in 2010. They concluded that nearly half of Americans ages 44 to 55 were at risk for poverty by age 65.

"There are 39 million of us in that age group," she says. "We have a 49% chance of being poor at 65, which means the risk goes way up when we are 70, 75 or 80." The last time the U.S. saw old-age poverty this severe was before the Great Depression, she says.

In other words, it's not a moment too soon to start thinking realistically. "You're not going to have the traveling-around-the-country-in-a-$100,000-RV-and-golfing kind of retirement, but that doesn't mean you can't still have a good retirement, even if it doesn't look like what you originally envisioned," says MSN Money personal finance columnist Liz Weston.

Here are the five keys to pulling it off:

1. Keep your hands off your Social Security

Claiming Social Security early is a bad idea, and yet it's a popular one. Nearly half of retirees take Social Security benefits when they turn 62. They're probably leaving money on the table that could make a difference to them in 10 or 20 years.

What's the rush? Some people are disabled and have no options. Some are jobless. Others are tired of working. Many are scared because policy discussions about reforming Social Security make them believe -- incorrectly -- that, if they don't grab benefits now, they'll lose out.

That's a mistake, says Steve Vernon, an actuary and expert on retirement preparation who wrote "Money for Life: Turn Your IRA and 401(k) Into a Lifetime Retirement Paycheck."

The most drastic proposals for cutting Social Security wouldn't touch anyone now in their 60s, he says. The most aggressive plans would affect people who are now 58 or older. The most liberal plans begin with those who are now 53 or 54.

The choice on when to claim benefits can cost people tens of thousands or even hundreds of thousands of dollars. "It can mean the difference between a near surely successful plan and a failing plan in many, many cases," says Robert W. Stanley, a certified financial planner in Libertyville, Ill. He teaches classes on strategies for claiming Social Security.

Waiting helps you postpone spending the savings you do have. Also, the longer you wait, the bigger your monthly Social Security check eventually will be. Your cost-of-living increases will be bigger, too.

Working even a couple of extra years can make a big difference, Vernon says. If you're 58 or older, you'll receive 25% less every month by taking Social Security at 62 instead of 66. Younger people will lose even more.

On the other hand, you'll earn up to 76% more each month by waiting to claim Social Security at age 70, according to research by the Boston College Center for Retirement Research. You can check the effect effect of your claiming age on your own benefits with the early-or-late calculator from the Social Security Administration.

"This is basically your paycheck for the rest of your life," says Weston.

Even if you've been laid off, you'll come out ahead by waiting and working even part time. You need only to earn as much as Social Security would have paid.

"I would take any job. I'd work at Starbucks. I'd work at Home Depot or do some kind of part-time work. . . . Later, when you retire and get a higher benefit, you'll be really grateful you did," Vernon says.

2. Park your home equity

If you've got home equity, treat it as an old-age emergency fund, Vernon says. Delay tapping it as long as possible. You'll need it in your 80s or 90s for surprises like home repairs, escalating heating fuel costs, medical bills or hiring in-home help.

People in their 60s are taking out reverse mortgages too early and choosing expensive, higher-risk products, the Consumer Financial Protection Bureau warned recently. Watch out for shady sales pitches and high fees that can result in you losing your home.

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