Choose the right dress color. Traditionally, the mother of the bride's dress should complement the wedding party's colors. Therefore, bridal director for Nordstrom, it's best to wait until your daughter chooses the bridesmaids' dresses to begin shopping. See if you can get a swatch of their fabric to take with you — it will be super helpful when searching for a harmonizing hue.
Borrow from the venue, too. It used to be that mother-of-the-bride dresses followed a kind of uniform — a cocktail jacket atop an understated sheath. While you probably wouldn't wear a strapless dress to a church wedding, it might be just the thing for a beach ceremony. However, you can add a lovely wrap or, yes, even a jacket to that same dress and it instantly becomes chapel appropriate.
Get pretty just prior to the wedding. There aren't any special rules for mother-of-the-bride hair and makeup. Again, think elegant, understated, and appropriate and reflective of your style. As with the bridal party, you'll usually want to get a fresh mani and pedi the day before the wedding and have your hair and makeup done the day of. Whether you do this with the bridal party is up to your daughter.