(FORTUNE Magazine) – There's nothing like a chastening experience with one of Wall Street's minions to underline some enduring truths. The broker had strongly recommended holding the stock of a takeover candidate at $91. Three weeks later it was down to $77, and he strongly recommended selling it. The client did so. Within nine days a takeover bid materialized and the stock shot up to more than $100. The client's cost was $56 a share, so he was still well above water -- but not nearly as much as he could have been. The family adviser who had urged realizing part of the gain at $91 was right: Don't be greedy. When you have a substantial profit, take at least some of it. Nobody consistently manages to buy at the low and sell at the high. As the Chinese sage Lao-tse said more than 2,500 years ago, if you give a man a fish, you feed him once, but if you teach him how to fish, you have fed him for the rest of his life. Accumulating wealth and passing it along to the next generation may be important, but so is passing along the principles of successful lifelong asset building. That guideline about profit taking is one of them. Here are nine more: -- Start early. A modest percentage of income put aside and invested can compound into millions over a working lifetime. -- Make common stocks the core. Few investments are as volatile, but historically few appreciate as much and keep you so far ahead of inflation. With mutual funds or individual shares, spread the risk among different industries, even different countries. -- Keep at it. If you buy stocks regularly, you'll sleep well whatever the market does. When stocks are low, you get more shares for the same money, and they're sure to go up again. -- Buy companies that do things better than anybody else. If they dominate their market, they may be high-priced, but good-quality stocks are like any other kind of valuable merchandise: Sometimes you can get them on sale. -- Watch the asset mix. Stocks, bonds, real estate, and gold don't all go up -- or down -- at the same time. When one of them gets so high that it bends your portfolio out of shape, take some profit and put it into whatever is cheap by comparison. -- Buy real estate where you know the values. Limited partnerships can get tricky fast. For a surer -- and simpler -- thing, buy the shorefront lot next door on Cape Cod or the wood lot up the road from your Oregon condo. Use REITs to diversify. -- Husband your borrowing power. If you're leveraged to the hilt, you'll be helpless when an extraordinary opportunity comes along. -- Don't confuse speculation with investing. The world's wealthiest people aren't traders but builders -- people who stayed in a business and reinvested in it. Anyway, if you trade a lot, commissions and capital gains taxes will kill you. -- Don't increase outgo dramatically when income rises. The more you spend on the country club and round-the-world cruises, the less you'll have from your highest-earning years for your retirement, your heirs, and your charities. As this fifth annual Investor's Guide special issue went to press, a stock market that in late summer had broken through the pre-crash high for the Dow Jones industrial average was regularly setting new records. Few seriously feared that the bull would fall off the cliff again soon, but few individual investors were buying aggressively either. It was a time to study the horizon and to pick investments with unusual care. To help FORTUNE's readers do just that, the 1990 Guide proposes both broad principles and specific tactics. The first section of the issue, Investment Strategy and Vehicles, opens with an expanded version of FORTUNE's quarterly Personal Investing report on what to do now, followed by a more extensive discussion of ways to maximize financial assets over a lifetime. You'll find advice on what to do if a bear market comes, and you'll meet a dozen bell- ringing young money managers. Some of them could be the next Warren Buffetts. In Five Investment Portfolios you'll learn how the pros think a group of different hypothetical households should allocate their investments -- and what specific stocks, bonds, mutual funds, and other securities they should buy. The Outlook section provides a Fortune Forecast tailored specifically for investors, picks seven industries (and companies in them) that look promising for 1990, and suggests a few others that you might better avoid. Taxes and Investing tells how to pass along as much of your assets to your heirs as possible and how to get the most from the changes Congress is making in the tax laws. The final section, Sources of Help, reports on a group of money managers with good track records who take on accounts as small as $25,000 or $50,000. It also looks at discount brokers and how best to use both them and their full-service brethren. That whipsawed client who was talked out of taking his profit fast enough negotiated 35% off the usual full-service commission, but even so his broker's advice cost him plenty.