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NEW YORK (CNN/Money) - Have you been watching the market? It's been crazy. The Dow Industrials are down 100 points one day, then up 200 the next. The yin and the yang of the stock market could make anyone crazy.

If you're like most 401(k) holders, you have a majority of your retirement funds fully invested in stocks. How can you make sure your retirement savings can survive the market whiplash? Here are today's five tips.

While this wave may have you feeling shaky, remind yourself of how solid you felt a few weeks ago when the Dow was steadily moving toward the 11,000 level.

Highs and lows: Wall Street can be a rocky ride, but there is a reason people are invested in it. History shows that if you basically keep a diversified portfolio invested, you can make nice returns over time. Reacting to the daily volatility, however, can get you into serious trouble.

It's important to understand the science. Bail out of the market when it's low and you're left on the downside, with losses. Buy in when the market is high, and you've left yourself with no room for gains.

The saying in Investment Finance 101 is "Buy low, sell high." While it's easy to say, it's hard to put into practice because it involves a lot of speculation. Your best strategy is to stay in for the long haul. In saving for retirement, most people have some time to ride out the little waves, and avoid the buying and the selling during the daily market swings.

Stay engaged with your 401(k). If the market is not offering you any appreciation, you need to be the one who builds up your nest egg. Just by adding money into your 401(k), you're getting returns because your contributions were pre-tax. Fundamentally, you're making a 20 to 30 percent return on the bit you took from your paycheck.

You know that cousin: the one with the hot stock tips? While it is possible to make some serious dough buying and selling shares of one company's stock, you also could lose a lot of money.

Taking advice from others can be tricky and often doesn't work. They might tell you when to buy, but eventually, you might not know when to sell. Experts say timing the market is nearly impossible.

"Unless you're a certified financial planner with 20 years experience, there's no sense in buying single company stocks," says Doug Flynn, an actual certified financial planner. Again, no one knows what's going to happen next, not even experts.

Buying mutual funds is a good way to downsize the risk of individual investments by spreading your money across several different types. With diversity in your portfolio, you don't have to worry about timing the market.

Fund managers monitor sectors in order to adjust their allocation appropriately to bring you returns. However, remember your investments are not on autopilot to fly off the charts with gains. Some funds continuously underperform.

It's your job to perform check-ups every now and then to clean out the bad ones. Riding out a mismanaged fund could hurt your potential earnings. To check up on the performance of your funds, check out the funds page at CNN/Money.com or Morningstar.com.

How do you know when to dump a fund? One rule of thumb: if your fund has underperformed its peers by the end of the second year, it's probably time to fold on that fund. However, if all the other funds in its class had similar returns, it could just be a bad time for those kinds of funds.

Another thing to watch with mutual funds are the fees that come with them. Several funds have earned bad names in recent years as investors were being charged excessive fees. Fees reduce your returns.

Altair Gobo, certified financial planner and partner at U.S. Financial Services in Fairfield, N.J., advises you to look at the expense ratio of your funds, which can be found on the CNN/Money.com funds page or at Morningstar.com. Gobo says you want a low expense ratio, below 1 percent is great. However, he warns that not every fund with low fees outperforms the rest.

In other words, your ideal approach to shopping mutual funds is to seek out top performance first. Once you find the best in class, choose the one with the lowest fees.

It's very easy to become unnerved during a wobbly stock market. But try to remember that weakness in stocks doesn't mean your retirement is down the toilet.

For one thing, homeowners, take some credit. Whether you retire in the home you currently live in or one five states south of you, your present home will play a big role in your retirement, says Gobo.

If you do decide to stay in your home, paying off your mortgage will give you a place to retire for nearly free (don't forget maintenance and property taxes). If you move to Florida for your golden years, you can use the equity you built in your present home to afford that pleasure.

Gobo did offer one caveat: like all markets, real estate has its good and bad days.

"Where we are in this market now, we've had two to three good-actually spectacular years This can't go on forever."

That doesn't mean the glory days will end tomorrow and you need to rush and sell your house. Timing the real estate market is also a toughie.

Gobo says, "If I built equity in my home and had a fair mortgage, I'd feel good about that investment." A fair mortgage, according to Gobo, means you own half your house or more. Like most financial markets, you are likely to weather many storms over time and still come out ahead.

Money 101: Investing in stocks

Money 101: Investing in funds

Gerri Willis is a personal finance editor for CNN Business News and the host for Open House. E-mail comments to 5tips@cnn.com.