Generally, the highest lifetime return to be had from Social Security benefits is to wait until you are age 70 to begin taking distributions. This is due to the 8% automatic annual increase in benefit payments when the start is delayed to that age, and the fact that most of us will live past their early 80s when the amount received from taking benefits later outstrips that of taking them at the typical retirement age.
If you decide however to start SS benefits before age 70 for whatever reason, an individual should never take them before full retirement age ("FRA," currently age 66) unless in serious financial need, or in cases where a normal life expectancy is not anticipated.
For married couples, the higher earner should wait to age 70 to begin taking benefits. This is because they will earn that higher benefit both for their lifetime and for that of their surviving spouse. There is no further advantage to be had by waiting until after age 70 to start taking benefits.
An advantageous approach for spouses is for the younger of the couple to take spousal benefits at FRA. To make this possible, the older spouse will have to be over FRA him or herself and be receiving benefits already, or if not yet age 70, to "file and suspend" for their own benefit. This arrangement allows one member of a married couple to take spousal benefits at FRA while allowing both of their primary benefits to continue to increase until age 70.
These are the general guidelines I use in my practice, though the reality is that the rules are complex and each situation needs to be evaluated individually. These guidelines do not necessarily apply to survivor benefits for spouses or children, benefits for divorced spouses or disability, all of which are beyond the scope of this outline. Also, note that you will need to enroll in Medicare at age 65, regardless of whether you start taking SS benefits.