By the time you're 65, you'll need to have socked away about $25 for every dollar you expect to withdraw annually. That means that throughout your working life you must save. And save. And save. Oh, and don't forget picking investments and managing your portfolio year in, year out. Yet with one simple act, you can take care of all of that work.

The Easy Way: Buy a target-retirement fund in your 401(k) A 401(k) is nothing if not easy: Contributions come out of your paycheck before you can spend them. You don't owe taxes on the money you invest, and earnings grow tax deferred. Sign up and aim to save 10% to 15% of your salary (including the company match).

Target-retirement funds, which are becoming one of the most popular 401(k) choices, are the ultimate in hands-off investing. You simply pick a fund with a date that matches the year you plan to retire - 2010, 2020, 2030 - and you get a completely diversified mix of stocks and bonds that's appropriate for you. This no-brainer fund automatically shifts stock assets into bonds each year, becoming more conservative as you age.

A target-retirement fund is a case in which simpler is actually better. Sure, you can come up with a smart allocation and pick top funds, but 401(k) investors often do a lousy job at that. What these funds give you is a disciplined plan, the key to retirement success.

By Kate Ashford, Carolyn Bigda, George Mannes, Walter Updegrave and Penelope Wang