Most major companies offer a 401(k) plan for employees -- but not all such plans are alike. From the amount of matching funds employers offer to the quality of the stocks and funds available, the variations among 401(k)s can make a huge difference in their participants' returns.

Here are some of 2009's highest-rated plans, courtesy of the folks at BrightScope:

Company

Overall Quality

Company Generosity

Investment Menu Quality

Southwest Airlines (NYSE:LUV)*

87

Great

Below Average

Charles Schwab (NASDAQ:SCHW)

86

Great

Above Average

ExxonMobil (NYSE:XOM)

86

Great

Great

Amgen (NASDAQ:AMGN)

86

Great

Above Average

Nucor (NYSE:NUE)

86

Great

Below Average

BP (NYSE:BP)

85

Great

Great

Pfizer (NYSE:PFE)**

85

Great

Average

Data: BrightScope. Overall quality rating is as reported in BrightScope rankings. Other categories as of Jan. 14.
* Pilots' plan.
** Pharmacia savings plan.

I didn't want to include the top-rated Saudi Arabian Oil Company (score: 93), because its plan might make you cry. It matches 100% of employee contributions, up to 9% of salary. Strangely enough, one area where it failed to get top ratings was in employee participation rates -- you'd think that more employees would take advantage of such a generous plan.

Unless you're looking for a new employer -- sorry, no word on whether Saudi Arabian Oil Company is hiring -- there may not be much you can do to change your plan. Still, you might be able to talk your employer into boosting your own plan's quality with the sort of features the best plans offer.

If you can't change the plan, change the performance
Whether you're stuck with a lackluster plan, or enjoying one of the best on the above list, the following 401(k) tips can help you achieve the greatest returns.

First, think twice before plunking much or most of your money in your employer's stock. While you probably do know more about that company than any other, you're already collecting most or all of your income from your current employer, which means you're already financially dependent on it. By spreading your 401(k) dollars among other terrific choices, you'll reduce the risk of completely wrecking your finances in the unlikely (but still possible!) event that your employer goes belly-up.

Second, consider maxing out your 401(k) to achieve the greatest long-term growth. I don't just mean contributing enough to get the maximum company match; unless you enjoy leaving free money on the table, that one's a no-brainer. But why stop at just 3% or 6% of your income? Upping that percentage to 10% or even 15% will make a huge difference in the wealth you can amass over time.

Third, tend to your investment selections. If you park all your money in conservative investments, it probably won't grow very quickly. If you're close to retirement, you probably want that sort of safety. But if you've got decades to go until your golden years, you should probably take at least a bit more risk, in exchange for the chance of better returns.

Finally, don't cash out of your 401(k) when you change jobs. You'll lose a hefty chunk of any payout to taxes, and the power of compounding interest means that even the loss of a relatively small amount now could blow a big hole in your future returns. Instead, talk to your new and old employers' HR departments about rolling your old 401(k) into a new one, or transferring it to an IRA.

Your 401(k) is just one component of the big picture when it comes to your retirement. But if you take the time to treat it right, you'll be that much closer to a happy, prosperous set of golden years.

For more on investing for retirement:

Spend some time in our Retirement Center to learn more, or check out our Rule Your Retirement newsletter. It's chock full of practical advice and great stock and fund recommendations, and you can try it free for 30 days.

Longtime Fool contributor Selena Maranjian owns shares of Amgen. Pfizer is a Motley Fool Inside Value pick. Charles Schwab is a Motley Fool Stock Advisor recommendation. Try any of our investing newsletters free for 30 days. The Motley Fool is Fools writing for Fools.