Chances are, you have a 401k plan at work. And the chances are, you're not making nearly enough of it. Now is as good a time as any to start turning that around.

If you're letting your 401k languish, a recent report shows that you're not alone. According to the Employee Benefits Research Institute, a think tank in Washington, most of us continue to neglect our 401k plan. The median account contains a balance of just $18,000, says the EBRI.

Good luck with that.

Here's a five-step plan to fix your 401k.

1. Take control

Take a look at the full range of investment choices available to you. That should include, at a minimum, a handful of low-cost domestic and international stock and bond funds. If your plan doesn't offer even those you should talk to the people in charge at your employer and insist that they move to a better plan.

Many people are too intimidated, or busy, to choose their portfolio. If you're in that camp, your plan will have dumped your money into a default portfolio -- such as a low-yielding but "stable" fund, or a target-date fund ostensibly designed for someone of your age.

There is nothing inherently wrong with these funds. But that doesn't mean you can rely on them, either.

These default options aren't designed for your best interests, but for the best interests of your plan provider. Instead of maximizing your likely returns, they are designed to minimize the provider's risk of a nasty lawsuit.

As a result, your money may well be sitting in a poorly designed portfolio that guarantees mediocre performance. Target-date funds, for example, are a great idea in theory. In practice, most are far too heavily weighted toward U.S. stocks, and they use a cookie-cutter approach to investing.

Consider the alternatives available to you.

You also should understand if your company makes matching contributions, and, if so, how much it will match. There's no good reason for missing out on a company match. It's also a good idea to find out if your plan allows such things as personal loans: This may offer you access to cheaper capital than you can get from a bank, although there are risks in borrowing from your plan.

2. Cut your costs

Many 401k plan providers stock their plans with high-fee mutual funds. That's great for them, and bad for you. Most mutual funds are far too mediocre to justify hefty fees, which just soak up a lot of your investment returns. A fund that charges you an extra 1% a year may end up costing you most of the tax benefits of your plan.

There are managed investment funds out there that are worth the money, but few of them -- if any -- are likely to find their way into a 401k plan.

If you're stuck with plain-vanilla funds, you are going to be better off going for the ones with the lowest costs. Nearly all the time your best options will be the low-cost index funds.

3. Lighten up on US stocks

Most people keep most of their stock-market investments in the United States. It's safer, right? I mean, it's the home market so it's less risky than foreign stocks, yes?

That's what conventional wisdom says, but it's hooey. Investors sell themselves short by investing too much in the U.S.A. You're already overinvested here anyway -- you have your life and career here.

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And U.S. equities are looking relatively expensive. U.S. stocks today are somewhere between modestly and heavily overpriced when compared with such metrics as average earnings or the value of corporate assets, according to data from the Federal Reserve and data tracked by Yale University economics professor Robert Shiller.

The dividend yield on the Standard & Poor's 500 Index ($INX), recently at just 2.1%, is very low by historical standards.

Predicting future stock-market returns is notoriously difficult. But based on current valuations, the U.S. stock market seems to offer a mediocre bet.

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