(MONEY Magazine) – In an ideal world, we'd start planning and saving for retirement the day we land our first job, and we wouldn't let up until we grab the gold watch and exit the work force for good. In the real world, life doesn't exactly turn out that way. More than half of workers age 55 and older haven't yet calculated how big a nest egg they'll need to retire comfortably, and over a third aren't saving any money toward that goal. Even those of us who've been more conscientious are likely to find ourselves playing catch-up in the years before we retire. The median 401(k) balance for people in their fifties, after all, is just over $53,000--not exactly the foundation for a cushy retirement.

You can, however, make up for lost time by making a few key moves in the critical decade before you retire. These three steps offer the biggest payoff.

With an aggressive savings program, you'll be surprised by how quickly you can bulk up your nest egg, as the projections at right show. Granted, saving 10% of your income, let alone 20%, is no easy task. But this is your last shot at feathering your nest, and chances are you'll never earn more than you do now. So pull out all the stops and be as disciplined and resourceful about saving as possible.

Your first step: Take advantage of catch-up provisions that allow those 50 and older to sock away extra money in retirement accounts. This year you can save an additional $4,000 in your 401(k) ($5,000 in 2006) and $500 in an IRA ($1,000 next year). Yet fewer than 25% of eligible participants use this option.

How do you come up with the extra cash? Do what you must. Direct all raises and bonuses into retirement accounts, spring for a basic, dependable car rather than a status-mobile, scale back vacations, boost your insurance deductibles and eat out less often. If reining in spending isn't enough, take on freelance work or even a second job to generate extra cash.

The percentage of retirement-age households with more than 40% of their income going to credit cards and other loans nearly doubled to 14% between 1995 and 2001 (the latest figure available). Don't let yourself be among them.

To avoid piling on new debt in the years leading up to retirement, you may have to make hard choices, such as putting the brunt of borrowing for college on your kids. Also step up repayment of existing loans. Start with your high-rate plastic, then move on to car loans and 401(k) loans, if you have them. Next, shift to paying off your home-equity line of credit, since paring that balance will free up more of your home's value as a resource you can tap later in retirement if needed. Making extra payments on your home mortgage to retire the loan ahead of schedule makes sense only if you can do so while also still building your savings.

To quickly supersize your portfolio's value, you may have to defy the conventional wisdom about lightening up on stocks as you near retirement. But that doesn't mean taking on kamikaze risk. Rather than homing in on, say, high-octane tech stocks, focus instead on stable blue chips and dividend-paying companies with a modest helping of small, fast-growing firms. Complement those stocks with short- to intermediate-term bonds that will add ballast during market squalls and will hold up better than long-term issues if interest rates rise.

Taking these steps won't guarantee you a financially secure retirement, but it will certainly improve the odds.

By saving aggressively in the decade before retirement, you can add mightily to your nest egg. The projections below are for an employee now making $70,000 who gets 3% annual raises and a company match of 3% of his salary on 401(k) contributions, and who earns 8% a year on the account.

SOURCES: T. Rowe Price, MONEY research.