8 rules of thumb on saving and retirement

The rule: To make sure your retirement lasts, never withdraw more than 4 percent a year.

Why it works: This simple formula has proven accurate over time, helping people easily figure out a guideline for how much they should withdraw so as not to exhaust their retirement savings, says Baughman.

Grain of salt: Be sure to track how your portfolio is doing. If it takes a hit, adjust your withdrawals downward. Withdrawing 4 percent of what your portfolio used to be worth is a good way to deplete it quickly, says Pomeranz.

Finke says another potential danger is that you won't live long enough to justify withdrawing only 4 percent of your savings, and that you'll miss out on taking vacations, making charitable contributions and giving gifts to family members. Finke says a better solution may be to use part of your retirement funds to buy an annuity or other insurance product to provide a base of lifelong income, allowing you to draw from your retirement funds more freely.