Roth IRAs and Roth 401(k)s are two retirement accounts from which people are not required to withdraw at a given age, according to the IRS, since the contributions were after taxes.  

If a person continues working, he does not have to make a withdrawal from a retirement account maintained by his employer. But he must make withdrawals from any accounts from former jobs that have not been rolled over into the current employer's account, Reichenstein says.

Reichenstein and William Meyer, a Social Security specialist and author of How to Optimize Retirement Benefits, have developed www.ssanalyzer.com to help determine the best way to take benefits.

Minimum withdrawals must be made from all other accounts, although the total needed to be withdrawn can be taken from a single account, according to the IRS.

"You might want to sell a stock in a portfolio that is not performing well to meet the minimum withdrawal requirement," advises Locker.

The money withdrawn can be used for a charitable donation and count as the minimum withdrawal, but only if it is the first money taken from the account that year. If part of the minimum withdrawal has been taken earlier in the year, a subsequent withdrawal cannot be used as a charitable donation and count toward the minimum.

Withdrawals can be taken periodically throughout the year or in a lump sum. Investors may want to leave the money in the account as long as possible so it continues to grow.

Advisors also should take into consideration the emotional factors when weighing when their clients should take withdrawals and pay taxes, says Christine Fahlund, CFP, and a senior financial planner and vice president of T. Rowe Price Investment Services.

"Advisors should be talking with their clients about when they feel the most pain paying taxes," says Fahlund. "Sometimes people feel more pain paying taxes after they retire, so they should take withdrawals before they retire and go ahead and pay the taxes.

"That is the emotional side of the question," she says. "Maybe they should take part of the money and practice retiring while they are still working part time. That is where advisors have to listen to clients."