Music geek that I am, I'm a big fan of the BBC's "Desert Island Discs" game: If you were stranded for the rest of your life, which eight albums would you want for company?

Investing geek that I am, I can't resist changing the question and raising the stakes: If you could make only one investment for the rest of your life, how would you proceed?

Better living through cheating
Me? I'd cheat. When it comes to music, box sets like, say, AC/DC's Bonfire are the only way to go. And with investments, mutual funds should be your vehicle of choice. Why place all of your hard-earned moola on a single horse when you can spread your bets around and sleep peacefully with a set-and-forget portfolio built on a clutch of poised-to-outperform stocks and top-notch mutual funds?

On that latter front, Vanguard 500 Index (VFINX) and the SPDRs (SPY) exchange-traded fund (ETF) are perfectly viable options -- low-cost S&P 500 trackers that rise and fall with a benchmark that counts General Electric (NYSE: GE), Coca-Cola NYSE: KO), and Apple (Nasdaq: AAPL) among its top holdings.

And these days, of course, you can easily track other bogies. Value hounds may gravitate toward iShares Russell 1000 Value (IWD), an ETF that specializes in companies with lower price-to-earnings ratios, like Home Depot (NYSE: HD) and Chevron (NYSE: CVX). If you're looking for a growthier vehicle, that's not a problem, either. The iShares Russell 1000 Growth (IWF) ETF is a simple way to dial up your exposure to racier plays such as Google (Nasdaq: GOOG) and Monsanto (NYSE: MON)), both of which boast five-year earnings-growth forecasts in excess of 25% annually.

But investing in even rock-solid index funds means that you're destined to lose to the market: The most you can realistically expect is for your funds to lag their benchmarks each year by about the amount of their expense ratios.

The good news
Fortunately, you can do better than that -- much better. There are world-class actively managed funds out there with fortunes that aren't tied to an index and managers who have shellacked the market over the course of many years. The question is how to find them -- and how to combine them with your existing stock holdings in a way that makes dollars and sense.

In terms of funds, here's a tip: I've found that focusing on managerial tenure goes a long way toward helping you zero in on a short list of worthies. A fund may have a stellar track record, but if the stock-picker who earned those high marks isn't still in charge, that performance history doesn't tell you a thing about the fund's forward-looking prospects.

A fund's price tag is a critical piece of the puzzle, too. Expense ratios come right out of your returns. All else being equal, the lower they are, the bigger your nest egg.

But all else isn't equal
There are plenty of other variables, and considering them all (so you don't have to!) is a big part of the job we do for members of the Fool's newest investment service, Ready-Made Millionaire. The centerpiece of our service is a compact, set-and-forget portfolio of just eight names: three world-class mutual funds, four growth-at-a-reasonable price stock picks, and an ETF that targets an area that resides near the market's valuation sweet spot just now. Our aim: to whip the market over the next three to five years and beyond.

RMM will open to new members next month. Between now and then, we invite you to learn more about the service -- and to snag a special free report -- by clicking right here. The report, dubbed The 11-Minute Millionaire, serves up a clutch of tips designed to help you navigate up markets and down.

This article was originally published on October 3, 2006. It has been updated.

Shannon Zimmerman runs point on the Fool's Ready-Made Millionaire service. At the time of publication, he didn't own any of the securities mentioned above. Coca-Cola and Home Depot are Motley Fool Inside Value recommendations. Apple is a Stock Advisor selection. Google is a Rule Breakers choice. The Motley Fool owns shares of SPDRs. You can check out the Fool's strict disclosure policy by clicking right here.