There are different ways for couples to go about using their monogram.
(Via Emily Post’s Wedding Etiquette by Peggy Post, 5th edition:)
For a married couple (Let’s say Emily Smith and David Pealer) sharing the same last name, Pealer, the monogram would read: E P D (with the center initial larger than the others.)
For a married couple with a hyphenated last name, it would read: E S-P D
For a married couple where the wife keeps her maiden name, the monogram would read: S * P. The S for Smith and the P for Pealer could be separated by a shape, dot or another design.
A few common places to incorporate the couples’ chosen monogram: Favors (tags, boxes or favors themselves such as cookies, chocolates), on the wedding cake, Gobo on the dance floor or on another surface at the reception, invitations, thank you stationary, cake topper, or on registry items such as towels, sheets or water glasses.
~ Karen Peterkin, Wedding Day Director