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At a time when most people don't have a traditional pension, protecting your 401k balance is essential to a secure retirement. Pay close attention to 401k rules to make sure fees, taxes and penalties don't bite into that balance. Here are 10 ways to make the most of your 401k plan:

Don't accept the default savings rate. New employees are increasingly likely to be signed up automatically for a retirement account at work, most often by having 3% of their pay deposited in their company's 401k plan. But saving 3% of your salary, while certainly better than not saving anything, may not be adequate to fund your current lifestyle in retirement.

"For a lot of people, that is not going to be enough," says Michele Clark, a certified financial planner for Clark Hourly Financial Planning in Chesterfield, Mo. "When you get a raise, save 1% more every year until you can get up to hopefully 20% of your pay."

Get the full match. The most common 401k match is 50 cents for each dollar saved up to 6% of pay. If your employer offers a 401k match, make sure you save enough to take full advantage of it. Capturing a 401k match is one of the fastest and easiest ways to boost your 401k balance.

Stay until you are vested. You won't get to keep the 401k match from your employer until you are fully vested in the 401k plan, which can sometimes take as long as five or six years of employment at the company. Some employers allow people who leave before they are fully vested to keep a portion of the match based on their years of employment, while other companies require workers who leave before the vestment period to forfeit the entire match. It can sometimes be worth thousands of dollars to continue to work for a company until you are fully vested in the 401k plan.

"If you are in a miserable employment situation or have a life-changing opportunity to go somewhere else, maybe you have to sacrifice the unvested portion," says Joel Kelley, a certified financial planner for Woodstone Financial in Asheville, N.C. "If you are considering a lateral move careerwise, you should definitely take that into account."

Maximize your tax break. Traditional 401k plans allow you to defer paying income tax on the money you save for retirement. Investors can contribute up to $17,500 to a 401k plan in 2013, up $500 from 2012. After age 50, the limit jumps to $23,000. Low-income workers who earn less than $29,500 for singles, $44,250 for heads of household and $59,000 for couples in 2013 and save in a 401k plan can additionally claim the saver's tax credit, which is worth up to $1,000 for individuals and $2,000 for couples.

Diversify with a Roth. A growing number of employers now also offer a Roth 401k option, in which workers can save after-tax dollars that are distributed tax-free in retirement. A Roth 401k generally offers the biggest benefits to young and low-income workers who expect to be in a higher tax bracket later on in their career, but it can also add tax diversification and flexibility to the portfolios of people closer to retirement.

Don't cash out. Most workers switch jobs several times over the course of their careers, which means they routinely need to decide what to do with the 401k balance at their former employers. It can be tempting to withdraw the cash, but workers who withdraw money from their 401k account before age 59 1/2 face a 10% early withdrawal penalty and income tax on the amount withdrawn. Early withdrawals also cause you to miss out on valuable compound interest, which is essential for building a large nest egg. "This money needs to be put away for retirement, and that's all it needs to be used for," says Carolyn McClanahan, a certified financial planner for Life Planning Partners in Jacksonville, Fla.

Do a fee-free 401k transfer. When you change jobs, you can generally leave your 401k balance at your former company or roll it over to an IRA or your new employer's 401k plan. If you decide to move your money, ask your former employer to directly transfer the balance to the new financial institution instead of cutting you a check. This will help you to avoid taxes and penalties.

Minimize fees. Investment options with high fees will significantly reduce your 401k balance over the course of your career. "Some 401k investments have very high costs, and you should pick the lowest-cost investment in your 401k plan that also matches you risk tolerance," says McClanahan. "If it's a high-cost 401k plan, then maybe consider saving in an IRA instead of the 401k after you get the match."

Workers now receive more information about the fees being deducted from their retirement accounts, thanks to new Labor Department rules. "If the funds are bad and the fees are high, start making noise to your human resources department and see about getting the plan changed," says Clark.

Diversify your assets. Choose a mix of stocks and funds that is appropriate for your risk tolerance, and periodically rebalance your portfolio to your target allocation. "As you approach retirement, shift a portion of your 401k to less-volatile mutual funds to preserve your capital," says Clark. But avoid making significant changes to your investment strategy on a whim. "The worst thing that you can do besides not participating is to attempt to time the market or change your investments every time you hear some economic news or story that could impact the market," says Kelley. "Stay the course."

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Remember required minimum distributions. After age 70 1/2, you are required to take annual distributions from a traditional 401k (but not a Roth 401k). The penalty for failing to withdraw the correct amount is a stiff 50% of the amount that should have been withdrawn. Make sure you take required minimum distributions each year in retirement to avoid the penalty.

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