BUY THREE INDEX FUNDS. Take the money you want to invest and funnel half into the Vanguard Total Stock Market Index Fund, one quarter into the Vanguard Total Bond Market Index Fund, and one quarter into the Vanguard Total International Stock Index Fund, or substitute similar funds from Fidelity, Schwab, T. Rowe Price, or several other mutual-fund families. With these three funds, you've bought a piece of nearly every stock and bond in the world worth owning.

INVEST A FIXED AMOUNT (WHATEVER YOU CAN COMFORTABLY AFFORD) EACH MONTH. The easiest way is to have the money transferred from your bank account through an automatic investment plan.

CHECK THE VALUE OF YOUR FUNDS QUARTERLY — NO MORE AND NO LESS. If you check more often, you'll be tempted to sell at the bottom and buy at the top. Remember: A watched fund never simmers.

NEVER TAKE ANY MONEY OUT— unless you have a legitimate and pressing need for it (college tuition or a housing down-payment counts; jewelry and cruises don't).

ADD EXTRA CASH. Whenever you have a pinch of unexpected money, add it to whichever fund has performed worst over the past year. That way, you'll always be buying low, so you can sell high in the future.

REPEAT UNTIL FINANCIALLY SECURE.

TOTAL COOKING TIME: a decade or two.