Many couples today feel that the old, time-honored titration of the hopeful groom asking a parent's permission to marry her daughter is antiquated. If, however your daughter or her boyfriend or believes this tradition is a nice touch that will help cement in-law favor, be prepared with ideas about how to respond to your future son-in-law.
You might respond to the prospective spouse with some questions of your own, such as “Do you love her?” or “How does she feel about this?” It would be unfortunate for you to give your permission for your daughter's boyfriend to marry your daughter, when in fact, she may not want to get married -- or that she doesn't want to marry him. In another day and age, you might have asked if he was financially able to support her, but today, it is likely that a couple will need two incomes.
The question might give you pause if you think your daughter would bristle at the thought of marriage. When the hopeful groom asks you, you can try a little humor by asking if her hand is the only thing he wants. Once everyone has recovered from this, you can assure the prospective suitor that if your daughter agrees, it certainly would be foolish to stand in the way or to withhold your blessing. You can follow up with a few more questions, such as whether they have set a date or a location, or whether they plan to live after the nuptials.
Many couples live together for a time before they marry; it is like trying the relationship on for size. If your daughter and her intended are living together, you might quip that it is about time they decided to make it legal or how glad you are that they will finally tie the knot. If you’re curious as to why they are making the step now, you might ask what has changed, such as if she is pregnant, or if they have a better income, or if they simply felt that now "Is the right time to get married."
Some mothers don't want to believe that her adult daughter is fully capable of making the decision herself without the need for your permission. You can defer to your daughter and assure her and her intended that you will be happy for both of them, if it is truly what they want to do. You know it is up to her anyway, so asking your permission is a courtesy and not a requirement. You can ask your daughter how he managed to catch someone as beautiful and smart as she is or you can remark how happy they look together.