The issue of hidden fees in 401(k) plans has been getting attention over the past few years, and not a moment too soon. Getting your arms around what you're truly paying is tricky work, and clearly some plan sponsors aren't doing their part to create topnotch company-retirement plans for employees. Over the years, many of you have shared tales of expensive plans chock-full of subpar investment options.

If you find yourself in that boat, the next logical question to ask is whether you should even bother investing in a company plan that doesn't measure up. If you're not earning a match on your contributions, your first step should be to consider a Roth IRA or even a traditional deductible IRA before steering funds to a company plan that's a stinker.

But if you do determine that the tax-deferred nature of the company-retirement plan offsets its weaknesses, how can you make the most of that subpar plan? Here are some tips if you find yourself in this predicament.

1. Go the index route.
OK, so maybe your plan doesn't feature mutual funds managed by topnotch stock-pickers. But if the plan's options include index funds--offerings that track a given market benchmark rather than attempting to beat it--you can obtain broad market exposure at a reasonable cost. Even if the index funds in your plan aren't the best--say, your plan offers an S&P 500 fund from Dreyfus rather than the ultracheap options from Vanguard, Schwab, or Fidelity--you're probably still better off going the index route than you are opting for a lackluster active fund. True, the active manager--even the one with a subpar past record--has a shot at beating his or benchmark, at least in theory. In practice, however, the active fund's expenses--as well as transaction costs that aren't reflected in its expense ratio--weigh heavily on that manager's ability to beat the benchmark.

2. Take the best and leave the rest.
It's natural to want to craft a 401(k) portfolio that's diversified across all of the major asset classes (bonds and U.S. and foreign stocks), but that might not be practical or prudent if your company plan doesn't offer viable options in all of these areas. If your plan features a few standout options and the rest are subpar, load up on the few decent funds and avoid the rest. You can use your IRA, your taxable accounts, or your spouse's retirement plan to delve into those asset classes and investment styles in which your own plan is lacking.

For example, say the stock funds in your company plan are poor but the lineup does offer a top-quality core bond fund. Even though your overall asset-allocation plan calls for just 30% in bonds, you could sink a big share of your 401(k) portfolio into the bond fund and then go light on bonds in your other accounts.

The key to making this strategy work is to look at all of the assets geared toward a particular goal or time horizon in aggregate. Morningstar.com's Instant X-Ray can make easy work of this task. Just enter all of your retirement-related holdings into the tool, then click Show Instant X-Ray to see aggregate asset-class, investment style, and sector data for all of your holdings.

3. Investigate the brokerage window, but do so with care.
Increasingly, 401(k) plans--particularly those from large employers--are offering so-called "brokerage windows," also called "self-directed accounts." If your plan offers such an option, you'll have the opportunity to delve into hundreds of other mutual funds, stocks, and even exchange-traded funds that aren't part of your 401(k) plan's preset menu.

Having the option to choose from such a wide array of securities can be a godsend if your plan consists of pricey funds that are past their prime. Using your plan's brokerage window, you can gain access to some of Morningstar's off-the-beaten-path Fund Analyst Picks, and you may also be able to venture into exchange-traded funds, some of which carry rock-bottom expense ratios.

But before you jump aboard, be sure to read the fine print. You may pay an extra fee (often levied annually) to participate in the brokerage window, and those extra costs can quickly erode the extra returns you might gain by venturing beyond your plan's preset menu. In addition, you may pay separate transaction costs to buy and sell securities that are part of the brokerage window. (That will almost certainly be the case when buying stocks and ETFs, so if you're going to go this route, it pays to do so by investing a single lump sum rather than making a lot of small purchases.) Finally, using the brokerage window may require additional work on your part. Whereas most 401(k) contributions are deducted directly from your paycheck, thereby adding valuable discipline to the investment process, you may have to actively make the trades into investments via your brokerage window.

And while the brokerage window might give you the opportunity to venture beyond the plain-vanilla offerings that are often mainstays of company retirement plans, beware of loading up on niche offerings with extreme risks. Even though the brokerage window might offer an array of sector funds, niche bond vehicles, and region-specific international offerings and ETFs, large-cap stock funds and intermediate-term bond funds should still serve as the linchpins of your 401(k) portfolio.

4. Talk to HR.
If employees in your company are grumbling that the retirement plan is subpar, be sure to let your human resources department know how you feel. You may not be able to enact change overnight, because a lot of factors--not just the quality of investment options--figure into a company's decision to opt for one retirement-plan provider over another. (It's an unfortunate fact of life that some investment providers slash costs and offer employers other goodies to entice them to opt for substandard plans.) But your employer should still be aware that its benefits package isn't measuring up.

5. Check out other options.
If you've determined that your company plan is weak, that means you'll have to make the most of all of the investing options available to you, tax-sheltered and otherwise. Investigate whether you're eligible to contribute to a Roth or other IRA (Morningstar's IRA Calculator can help), and plan to max out your spouse's plan if it's better than yours. Also be savvy about investing in your taxable accounts; I'm a big fan of tax-managed funds, particularly those from Vanguard. Last but not least, recognize that your own savings rate is the most powerful lever you have in determining the size of your eventual nest egg.

A version of this article appeared Oct. 9, 2008.