Russian tennis star Maria Sharapova should be able to retire before she turns 30. Esther Bennett -- recently profiled in The New York Times -- is still working at a bus company at age 77, unable to afford retirement.

At the site 43things.com, more than 500 people have listed retiring early as a top goal in life, ahead of staying in touch with old friends, learning to play a musical instrument, meditating more, being a better sister, or going on a safari.

You probably won't be able to retire anywhere near the age Sharapova will be when she does. Fortunately, though, through a disciplined savings and investing plan, you may be able to retire sooner than you think.

The sooner you start ...
If you're 20 and you're reading this, there's a very good chance that you can retire at 50 -- and then go on a safari! All you have to do is save and invest regularly, starting today.

Suppose you save and invest $5,000 yearly beginning at age 20. Then increase that to $6,000 at age 25, $12,000 at age 30, $16,000 at age 35, $20,000 at age 40, and $25,000 at age 45. Provided you earn the market's historic average annual return of 10%, you'll end up at age 50 with nearly $1.7 million. (A low-cost, broad-market index fund can help you earn the market average.)

That $1.7 million can buy you roughly $8,000 monthly, via an immediate annuity -- providing nearly $100,000 in annual income. Voila -- early retirement!

But wait!
Suppose that in your case, retiring at 50 seems long out of reach? Take heart -- an early retirement still isn't necessarily impossible. But to retire sooner, you'll need to look hard at ways to improve your saving habits and investment performance.

For example, if you have your "investable assets" (cash you won't need to touch for at least 12 to 36 months) stashed in CDs earning 5% annually, you'll want to steer at least a portion of those assets into stocks or stock mutual funds that will offer better long-term returns. After all, $50,000 growing at 5% for 10 years will increase to a little more than $81,000. At 12%, it will nearly double that amount, growing to more than $155,000.

And how can you save more than you're already saving? First, if you haven't already, sign up for automatic savings withdrawals from your direct-deposited paychecks. That way, you can bulk up your bank account without even noticing most of the time.

Also look into ordering your prescription drugs by mail, because doing so can be considerably cheaper than going to your local drugstore. Shop around for the best deals when traveling. And even consider raising your deductible on your car and home insurance -- though never to a level beyond what you keep in your emergency fund.

If you can find the money
After you've found some new savings, you'll want to make sure all of your savings are stashed in the best and most appropriate places possible. Just look at what a difference just a few basis or percentage points can make to an investment of $10,000 over 25 years:

Growing at 

Becomes

6.0%

$42,900

6.5%

$48,250

8.0%

$68,500

8.5%

$76,900

10.0%

$108,300

10.5%

$121,400

12.0%

$170,000

12.5%

$190,000

14.0%

$264,600

14.5%

$295,000

This chart should prove just how important it is to get the best performance at the lowest price. After all, the 10 best mutual funds of the past 10 years not only offered great returns but also charged an expense ratio 20 basis points less than their average peer. Those 20 points make a difference!

Good funds aplenty
Bridgeway Aggressive Investors 2 (FUND: BRAIX) is just the kind of best-in-breed fund that can help you fund your retirement faster. It sports a five-year average annual return of more than 20%, and it charges 1.22% annually (cheap for its peer group). With holdings that recently included innovative names such as Apple (Nasdaq: AAPL), Garmin (Nasdaq: GRMN), Research In Motion (Nasdaq: RIMM), and Oracle (Nasdaq: ORCL), the fund is rather tantalizing. Potash (NYSE: POT) and AT&T (NYSE: T) are also major holdings.

Not for nothing, this Bridgeway fund is a recommendation in our Motley Fool Champion Funds service.

If you're looking for more mutual funds that can help you retire at 50 -- or soon after -- you can take a look at every fund we've recommended in Champion Funds free for 30 days. What's more, the service's model portfolios can help you build the optimal portfolio for your specific retirement timeline.

Even if you're not Maria Sharapova, it's never too late to kickstart your savings and investments. The key is to start now.

Longtime Fool contributor Selena Maranjian does not own shares of any company mentioned. Garmin is a Motley Fool Stock Advisor recommendation. Bridgeway Aggressive Investors 2 is a Motley Fool Champion Funds recommendation. The Motley Fool is Fools writing for Fools.