Have you socked away $100,000 or more for retirement? Odds are, you haven't. According to the 2011 Retirement Confidence Survey, fully 76% of Americans have saved less than $100,000. And it's actually worse than that -- 56% have saved less than $25,000. It may seem hard to save money, but once you learn about Oseola McCarty, you'll see how few excuses you have.

You see, McCarty managed to accumulate way more than the average American -- $280,000 -- while living in conditions much tougher than most of us. Born in 1908, she worked doing laundry for 75 years, having had to leave school in the sixth grade. She never earned more than $9,000 per year.

Her life offers many lessons to those of us who would like to build comfortable retirements. Here are a few:

It's easy to believe in the power of saving and investing. It's easy to intend to allocate 10% (or, ideally, more) of your income to a retirement account. But actually doing it can be hard -- or can seem so.

You can make it easier on yourself by taking your savings out of your paycheck immediately, before you spend that money. Better still, automate much of your financial life, having contributions automatically made to your retirement and savings accounts.

Stay the Course

While opening a Roth IRA or contributing to your 401(k) at work is indeed a good reason to pat yourself on the back, it's not enough. You have to keep contributing to them over time, with more money than you might want to contribute. If your employer is moving 3% of your salary into a 401(k), that's probably not enough. If you sent $2,500 to your IRA this year, that's probably not enough, either. Most of us are allowed to contribute up to $5,000 per year ($6,000 if we're 50 or older) to our IRAs, and the contribution limit for 401(k)s is $17,000 for 2012, plus an additional $5,500 for those 50 or older. To build a strong retirement account, you'll need to put away a lot of money over many years, if possible. McCarty certainly socked away as much as she could, for many decades.

Here's why you need to be aggressive and diligent -- especially if you're only a decade or two away from retirement: Imagine a $400,000 nest egg, which might seem sufficient to you. Experts don't agree on how much you should withdraw from your nest egg each year in retirement, but 4% is a common figure (adjusted for inflation). If you take 4% out of that $400,000, you'll have $16,000 in your first year. Coupled with Social Security, will that be enough for you to live on? Many of us will want to accumulate $1 million dollars or more, if we can.

The idea of $1 million might freak you out, especially if your savings account now has, say, $63,000. But all is not lost. There are ways to strengthen your position, besides saving more aggressively. You might downsize your home, for example. You could even take in a boarder, if it makes sense for you.

A simpler option is just to work longer. A few more years can make a world of difference. By delaying your retirement, you'll shorten the amount of time that your nest egg will have to last, and you'll have a few more years in which to beef it up. During your extra working years, you might enjoy health insurance from your employer, too, saving you some expenses.

McCarty maximized this approach, working until she just wasn't physically able to anymore, at age 86. Thus, her retirement was rather short. She actually ended up with far more than she needed, and she was able to give away about half her fortune, donating $150,000 to the University of Southern Mississippi in Hattiesburg.

A final lesson is that we should invest our money effectively. Ms. McCarty mainly used a savings account for many years, until her bank noticed her growing balance and suggested she use CDs and conservative mutual funds. That certainly helped her money grow faster, but she could have done even better.

If you save a lot but keep all your money in CDs and money market funds for decades, you'll be short-changing yourself. Long-term money, which you won't need for at least five years -- or, ideally 10 or more -- is likely to find its best returns in the stock market. You can tap that resource easily via a broad index fund such as SPDR S&P 500 (SPY) or the Vanguard S&P 500 Index Fund (VFINX).

Consider adding some individual stocks to your mix, if you're willing to do a little research and keep up with them. Johnson & Johnson (JNJ), Intel (INTC), PepsiCo (PEP), and Procter & Gamble (PG) are solid long-term performers, each recently offering a dividend yield over 3%. ExxonMobil (XOM) has been yielding more than 2%. Apple (AAPL) pays no dividend at this point, but it's sitting on a pile of cash and many expect the stock to keep growing for a good while. These companies are not without risk, but by diversifying your money, you can reduce the effect of any possible hit from one company.

Whether you're an executive with a six-figure salary or a public school teacher pulling in five figures, you can build yourself a more comfortable retirement. There's a good chance that a million dollars may even be within your reach.

Longtime Motley Fool contributor Selena Maranjian owns shares of Apple, Procter & Gamble, PepsiCo, Intel, and Johnson & Johnson, but she holds no other position in any company mentioned. The Motley Fool owns shares of Intel, Johnson & Johnson, PepsiCo, and Apple; has sold shares of SPDR S&P 500 short; and has bought calls on Intel. Motley Fool newsletter services have recommended buying shares of Intel, PepsiCo, Procter & Gamble, Johnson & Johnson, and Apple, as well as creating bull call spread positions in Apple and Intel, and diagonal call positions in PepsiCo and Johnson & Johnson.