20s
You've heard it before: The most important thing is to invest in a 401(k) or other retirement account, and if you can't afford to contribute $15,500 to your 401(k) (the 2008 limit), at least set aside enough to maximize the amount your company will match. The challenge is to pick the right funds. "Choose your employer's most aggressive 401(k) fund," says John Claghorn, at RBC Dain Rauscher (Suze Orman's financial adviser). "The biggest mistake people make is being too cautious, especially when they're young." Susan Burke recommends: "Make sure your 401(k) fund has both U.S. and international stocks. The U.S. economy is growing more slowly than others, so you need to be globally diversified."

30s
Now's the time to max out your contributions to your retirement accounts (if you haven't already). The easiest way to choose an appropriately aggressive retirement plan is to invest in a "life cycle" or "lifestyle" fund—one that automatically adjusts your holdings to less risky investments based on the number of years until you retire, says Suze Orman. For a rough idea of how much you'll need for retirement, Eric Tyson offers three scenarios:

1. You'll need 65 percent of your projected preretirement income if you save 15 percent of your annual income, are a high-income earner (generally more than $100,000), will own your home debt-free when you retire, and plan to live modestly in retirement.
   
   
2. You'll need 75 percent if you save 5 to 14 percent of your annual income and want to maintain your preretirement lifestyle.
   
   
3. You'll need 85 percent if you save less than 5 percent of your annual income, have to pay a mortgage or rent in retirement, and want to maintain your current lifestyle.
   
   

40s
If at age 26 you invest $20,000 and it earns 4 percent a year, it will grow to $95,000 by the time you reach age 65. If you wait until you're 46 to invest the same amount, it will grow to just $43,000. You've undoubtedly come across examples like this before to prove just how much more a person has to put away to catch up. The obvious advice from our panel to anyone who is behind in her savings is to spend less and save more, but John Claghorn has a further suggestion: "If you are going to be working for another two decades, and you are not going to be withdrawing money from your 401(k) or IRAs to buy a home or pay college tuition, invest as aggressively as you can tolerate."