You've probably heard that your retirement rests upon the three-legged stool of employer pensions, personal savings, and Social Security. Yet for most Americans, that last leg is the biggest and sturdiest (at least for now). The majority of seniors receive more than half of their income from Social Security; one fifth rely on Social Security for practically all of their income.

Given Social Security's prominence in most Americans' retirement plans, maximizing benefits is a top priority. Here are six lesser-known key facts about the largest slice of the federal budget.

1. The Higher Benefit Continues to the Surviving Spouse
   A spouse can claim Social Security benefits based on his or her own work record or receive half of his or her spouse's benefit, whichever is greater. When one spouse dies, the survivor automatically receives the higher amount. Generally, this has the largest effect on women, since wives tend to outlive their husbands.
2. Wives Should Take Social Security Early, Husbands Should Take It Late
   The sooner you begin to receive benefits, the less you'll receive. But wives should still consider taking their benefits early, because their benefits will automatically go up when their husband dies. The husband, on the other hand, should consider delaying benefits, since the longer he waits, the higher his benefit -- and it will continue to his wife after he's passed on.

   This strategy makes most sense when the husband is the same age or older than the wife and has earned more over his lifetime. Couples in which the wife is older or has earned more than the husband might benefit more from delaying benefits or having the husband take Social Security early.

3. Spousal Benefits Can't Be Claimed Automatically at Age 62
   A lower-earning spouse can't receive benefits based on the other spouse's record until the primary breadwinner claims benefits or reaches full retirement age. Also, spousal benefits don't increase if delayed beyond full retirement age, so spousal benefits should be claimed by then.
   However, that spouse can still claim benefits on his or her own work record at age 62, assuming he or she has earned enough credits (essentially, worked for 10 years). Finally, note that the penalty for taking early benefits is steeper for spousal benefits than it is for worker benefits.
4. Social Security Has Its Own Funky Taxation
   How much of your Social Security would you like taxed -- 0%, 50%, or 85%? We figure you'd prefer 0%, but large distributions from tax-deferred retirement accounts (as well as other sources of income) can cause up to 85% of benefits to be taxed. One strategy for keeping more of your after-tax benefits is to live off retirement accounts in the first few years of retirement and delay taking Social Security.
5. You Can Take the Money and Invest It
   You can take Social Security early but change your mind later to get the higher benefit. You need to submit a "Request for Withdrawal of Application" and give back all the money you had received from Social Security. One strategy is to begin receiving checks at age 62, invest the money, and then give it back at age 70 when you file form SSA-521. You get to keep what you've earned on that money without giving up the higher benefit of delaying until age 70.

   Important! Please note that the law has changed in the time since this was originally written. As described in this article, this "do-over" option is now only available for the first 12 months after filing for benefits. Thus, #5 of our 6 items has much more limited usefulness, starting in 2011.

For this to work, however, you must have the discipline to keep your hands off the money. Also, it doesn't make sense if you're still working between the ages of 62 and your full retirement age (65 to 67, depending on when you were born), since Social Security benefits are reduced if you earn above an exempted amount ($14,160 in 2011).

There are estate-planning issues, too. As noted earlier, a surviving spouse will inherit the lower benefit that comes with taking Social Security early (assuming it's still higher than his or her own). But the survivor can submit the request form, and the benefit will be estimated as if the deceased spouse had taken Social Security on the day he or she died.

Also, a single beneficiary who employs this strategy but dies before age 70 would have something to leave for heirs, whereas someone who planned to delay benefits but died before that time came would have no Social Security benefits to pass on.

6. Don't Delay Beyond Age 70
   Once you reach age 70, delaying benefits doesn't result in a higher monthly check. You should apply for Social Security even if you're still working. If your annual post-Social Security income is among the highest of your career (adjusted for inflation), your benefit will automatically go upward.