The mother of the bride traditionally plays a big role in the wedding, especially if she's hosting. Guests will come to you before, during, and after the "I dos" for information and help. Consider yourself a manager with a slew of responsibilities, including those listed below.
Have a meet-and-greet with the groom's parents.
If you've never met your future son-in-law's parents, take the lead and plan a get-together with them (as long as it's feasible from a travel point of view). It doesn't have to be a formal dinner—cocktails or even getting together for coffee would work. The point is to get to know one another before the wedding so you're not complete strangers on the day your children wed.
Go dress shopping with the bride.
You should be one of the select few who gets to see the bride in variations of tulle and silk-satins, or whatever she chooses to wear. It'll be an emotional time for you, and you'll know when she's found the right dress.
Stand in for the bride as the vendor go-to person.
This often happens if the bride is getting married in her hometown, where you still live but she doesn't. You should be prepared to answer any questions posed by the caterer, baker, florist, etc., if they can't reach your daughter.
Scout locations and vendors.
Again, this will happen if the bride lives far from the wedding site and you're local. Take direction from you daughter and lots of photos!
Let the groom's mom know what color and style dress you'll be wearing.
This is to prevent a fashion disaster where both moms walk down the aisle wearing magenta gowns with short sleeves and silver belts. Awkward! Your dresses' length and formality should match, though, so one of you doesn't show up in a short cotton dress and the other in a lace gown.
Support the bride's decisions.
Unless she wants to get married underwater and expects her 100 guests to get certified in scuba-diving, the bride should be the decider. Of course, if you're picking up the floral bill and hate yellow roses, which the bride was planning for the centerpieces, there's going to be some serious discussion going on. Try to compromise—maybe the bride could indulge in her favorite flower by having an all-yellow roses bouquet.
Offer up your shoulder to cry on.
Be there for her when the going gets tough, like when the bridesmaids are acting up or she finds out her first-choice photographer is already booked.
Help the bridal-shower hosts.
If you follow tradition, you're not supposed to host the shower, since the party's purpose is to bring the bride gifts (the idea was that it would be tacky for you to essentially be saying, "Bring my daughter nice gifts, people!"). But times have changed, and it's becoming more acceptable for the mother of the bride or a relative of the bride to be involved in hosting duties. You can offer to help with making decorations, food, or favor bags, or contribute to the shower without being named on the invitation.