Today's investors face some unnerving uncertainties -- high energy prices, a soaring federal budget, two economy-damaging hurricanes and a possible third on the way. Several experts are forecasting slower economic growth and cooler stock market performance on the horizon.

But don't let the latest predictions scare you into rejiggering your 401(k) or pulling out of the stock market altogether. Tune out the blaring TV stock pickers and stop kicking yourself for not buying Exxon last year. Instead, go to your quiet place and repeat, "long-term perspective, diversification, dollar-cost average, rebalance ... ohm."

That's right, you don't have to stress about your investments if you devise a solid plan and stick with it. Even if stocks pull back, you should continue to press forward. Trying to outguess the market is simply too gut wrenching, and foolish.

Mantra 1: Think long term

If you're looking at retirement 30 or more years away, or another major goal that's a decade or more in the future, then you have plenty of time on your side. And a long time horizon will help smooth out the market's day-to-day and year-to-year gyrations.

And stocks gyrate plenty. Over the last 30 years, the individual-year returns for stocks have ranged from -27% to +37% -- that's a spread of 64 percentage points -- according to Ibbotson Associates. Bonds tended not to dip as low or fluctuate as wildly over the same period. Their returns ranged from -7% to +43%. But over the long-term, stocks are always the clear winner. Since 1926, stocks have returned an average 10% annually, according to Ibbotson. Bonds, by comparison, returned less than 6% annually.

The longer you have until your savings deadline, the more risk you can afford to take. If your goals are decades away, consider putting all your money in stocks or stock mutual funds. You'll experience some swings in the market, but if you hold fast to your strategy, it should pay off in the end.

If 100% in stocks makes you a bit queasy, you can add some stability with bonds or bond funds. But don't put more than 10% of your portfolio in bonds if you have more than ten years to your goal. As your goal approaches, you will shift more money into bonds or cash, but now's not the time for that.

Your 20s and 30s are when you build the foundation of your wealth, and if you invest too conservatively now, you may severely hobble your growth potential over the years. For example, a single investment of $5,000 earning 10% each year would be worth $226,300 in 40 years. If your money earned 6% a year over those 40 years, you'd end up with only $51,400. See how much your money can grow over time.

Mantra 2: Diversify

This may seem like common sense, but it can be hard to discipline yourself, especially when one segment of the market is outperforming others. But if your investments are too heavily weighted on one stock or even one particular kind of stock, you can deep-six your savings goal. (Remember the tech bubble?) But this is where having a plan -- and sticking to it -- comes in handy.

Mutual funds are a good way to achieve instant diversification. One of the easiest and least expensive options if you're new to investing are "funds of funds" -- a single investment that holds a variety of other funds. Some will even tone down your risk automatically as you near retirement, such as Fidelity Freedom, Vanguard Target Retirement and T. Rowe Price Retirement funds. Learn more about this simple breed of investments.

If you have more money to invest, or are saving through your employer's retirement plan, consider spreading your money across funds that invest in each of the following:

• Large, fast-growing companies ("large-cap growth")

• Smaller, fast-growing companies ("small-cap growth")

• Large companies selling at bargain prices ("large-cap value")

• Smaller companies selling at bargain prices ("small-cap value")

• Foreign companies

Generally, you should aim to allocate 50% to 55% of your portfolio in large companies, evenly split between growth and value; 20% to 25% in small companies, even split between growth and value; and 25% in foreign companies.

Check out our sample long-term portfolio for specific fund recommendations. Or, use Kiplinger's Fund Finder to zero in on funds in each category that meet performance criteria you set.

If you choose to invest in individual stocks directly instead of through a mutual fund, use the same strategy, structuring your portfolio around those five types of stocks to spread the risk from the market's inevitable ups and downs. Kiplinger's Stock Finder can help with your research.

Mantra 3: Dollar-cost average

It's been said that the stock market runs on fear and greed. But these emotions are your worst enemies. It can be hard to convince yourself to put more money into your account when the market is tanking and your balance is going right along with it. But if you fail to invest during a down market, you miss out on low prices and may miss the rally when it inevitably comes.

It can also be rather tempting to plunk more cash into a fund that's performing much better than others in any given year. But if you overweight your contributions to one star fund, stock or sector, you throw your careful allocation out of whack and become more vulnerable to those unpredictable market swings.

A simple strategy called dollar-cost averaging can help keep your emotions in check. By investing a fixed dollar amount at regular intervals you smooth out the ups and downs of the market. Take out all the emotion and guesswork and investing becomes much less stressful.

Mutual funds are ideal for dollar-cost averaging because you don't have to pay a commission each time you buy. And, you can arrange with the fund company or your broker to have the money automatically taken from your bank account.

It's a good idea to invest once a month or once every quarter, depending on what your budget will allow. After you've made your initial investment, many mutual fund companies require your subsequent contributions be at least $100, though some will let you deposit less -- T. Rowe Price, for example, will let you contribute as little as $50 to your IRA. (Learn more about how to invest with little cash.)

Dollar-cost averaging with individual stocks or exchange-traded funds can get pricey, but it's still a good idea. However, you'll need to spread your investment intervals out to keep commission costs down, say, once a quarter or semester.

Mantra 4: Rebalance

The best-laid plan will inevitably get a little out of balance over time as one group of investments outperforms the others -- say, foreign stocks versus large-cap growth stocks. To restore your allocation, you'll want to rebalance your portfolio at least once a year.

While selling issues that are doing well may seem counterintuitive, rebalancing your assets helps you avoid investing on emotion and forces you to buy low and sell high, reducing the volatility of your portfolio and keeping your long-term investing strategy on track.

You should also re-evaluate your investment choices to make sure they still measure up. Learn more about knowing when it's time to cut a mutual fund loose or to sell your individual stocks.

MORE: Kiplinger.com | Investing | Column

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