Saving through a 401(k) plan – if it is done right – can make all the difference between a successful retirement and a less-than-successful old age. A recent survey shows that too many employees are not doing it right.

In the past 20 years, these plans have become the most popular means of retirement saving, partly because employers prefer them to the old “defined benefit” pensions. Their lifetime monthly payments of a fixed amount came with the job. In the 40l(k) plans, it is up to the employee to provide for retirement. He or she decides how much per month goes into tax-deferred account and how to invest the money. The employer often makes matching contributions.

But most employees are not skilled investors, even with whatever advice they get from their employers. In fact, a survey of nearly 1 million 401(k) accounts by Financial Engines Inc., a research and advisory company in Palo Alto, Calif., found that 69 percent of them had inefficient portfolios, inappropriate risk levels or both.

Some were inadequately diversified to even out the ups and downs of the market. Some were overly concentrated in the stock of the employee’s company, which can be part of a diversified portfolio but only in modest amounts. Some younger participants chose only the safest investments instead of relying on a rising market over the long haul. And some older participants invested too aggressively instead of choosing mostly conservative, low-risk securities.

Perhaps worst of all, one-third of the participants were not contributing enough through their 401(k)s to receive the full employer match, typically from 50 percent to 100 percent of what the employee puts in. Only 7 percent were contributing the maximum allowed. While saving a large portion of your salary is difficult, especially as living costs are rapidly rising, putting $100 into a 401(k) really amounts to saving about $128 because contributions to these retirements are not taxed.

Congress in 2006 allowed employers to automatically enroll workers in retirements plans, usually taking only a small percentage of salary and investing it in the most conservative fund. For workers who were not saving for retirement, this was a helpful step.

Now that most employees plan their own retirement, it would be helpful for employers to see that they get good advice on handling their investments. Financial Engines said a well-balanced portfolio of $30,000 would grow to more than $74,000 over 20 years with no further contributions. A poorly constructed portfolio for the same $30,000 would earn about $58,000 over those 20 years.

Above all, employees could be reminded that regular saving, even if it means giving up a latte or dinner out, can gradually create a nest egg that will make retirement a pleasure. That will be a lot better than a reduced standard of living or working a lot longer than they want to.