The Maid of Honour is the bride’s sister, cousin or close friend, who acts as the bride’s pillar of support, both emotionally and in helping her oversee wedding arrangements. If she is married, she is called the Matron of Honour.
Duties of the Maid/Matron of Honour (Some may not be possible if she's from out of town, in which case the bride may like to reassign the duty to another bridesmaid/honouree)
Assist the bride with addressing and sending out invitations
Assist the bride when she goes shopping for wedding-related items like her gown, florist, etc., in making favours and be available for the bride when she needs it.
Coordinate with bridesmaids and other female attendants regarding attire in terms of fittings, gown delivery, accessories, shoes, etc.
Host the bridal shower with the help of the bridesmaids.
Organize and contribute to the bachelorette party with the help of the bridesmaids
Coordinate on behalf of the bride (if she so designates) regarding the rehearsal as well as attend the rehearsal dinner.
At the wedding…
Help the bride to get ready
Help the bride manage her train, especially if it is cumbersome, arrange and display it effectively for photographs, ensure it does not catch or snag anywhere especially while walking down the aisle or at the reception and be familiar with how to bustle it/ detach it if required
Hold the bride’s bouquet during the ceremony, while she enjoys her traditional ‘first kiss’ and at other appropriate points and keep the groom’s ring safely until it is time to hand it over
Sign the marriage license as a witness
Stand in the receiving line
Raise a second toast to the couple (after the Best Man - optional)
Dance with the Best Man
Mingle with the guests, ensure they are comfortable
Get the bride refreshments, or a quick bite, so that she feels rejuvenated
Help the bride change from her gown to a going-away outfit and take charge of bridal gown
Gather souvenirs of the wedding as keepsakes for the bride if she so requests, for instance, toasting glasses, favours, take charge of guest book once all guests have signed, etc.