The best way to invest money in stocks or stock mutual funds, financial advisors like to say, is dollar cost averaging. That means adding money a little at a time in equal amounts.

Mathematically, the advisors are wrong. Averaging will probably cost you more money than you save. Yes, your equal payments will buy more shares when prices are low and fewer when prices are high, thereby ensuring you pay a below-average price. But that is more than offset by two tendencies. First, stocks rise twice as often as they fall, and second, over long time periods they tend to produce powerful returns. The cost of waiting with the bulk of your money is likely to eclipse the lower price you get with the rest.

Still, I d recommend averaging to just about anyone. It makes people feel safer, which is easily as important as tweaking their odds. And as with insurance, which is also a poor deal by the numbers (hence, the insurer s profit), averaging will once in a while protect an investor from an unlikely but catastrophic event--like the one the stock market has recently produced.

Now is an especially good time for averaging, which works its magic at price extremes and so is just the thing for volatility. Last year there were 18 days on which the market closed up or down more than 5%. That s as many as occurred between 1955 and 2007. This year seems as spastic. Mutual fund investors should by all means dribble new money in rather than dump it. Stock investors aren t as flexible. If they add $500 a week, trading commissions can eat up half a year s return. But stocks that pay generous dividends, when left to reinvest them, accomplish cost averaging on their own. In volatile markets, they can gradually shrink the holder s average price.

The companies below are good candidates for cost averaging. Emerson Electric (EMR) raised its dividend in December, its 52nd consecutive increase. The company sells a broad range of automation, precision control, power and climate-control equipment. About 40% of income comes from emerging-market customers that management says are still growing, albeit slower than in recent years. Sales are expected to decline 11% this fiscal year ended September, but Emerson is solidly profitable and only modestly indebted, and trades at an inexpensive 11 times earnings.

Waste Management (WMI) controls just over a quarter of North America s trash hauling. Most of its business is insulated from the economic slowdown, but some removing waste for homebuilders and manufacturers, for example has slipped. Earnings per share are expected to decline 8% this year. Shares are modestly priced at 12 times earnings, and a 4.5% dividend yield is more than covered by a free cash flow yield that s expected to top 11% this year.

On the table are details on these and three more companies.