Traditionally, these expenses are paid for by the Bride or her family:

• Bride’s and her mother’s attire
• Ceremony fees
• Flowers, including bridesmaids’ bouquets and floral arrangements for ceremony and reception
• Gifts for bridesmaids
• Gift for the groom
• Groom's ring
• Invitations and stationery
• Lodging for her out-of-town bridesmaids
• Musicians for ceremony and reception
• Photographer
• Reception costs (i.e. site, catering, rentals, etc.)
• Transportation for bridal party to ceremony and reception
• Videographer
• Wedding Cake
• Wedding Coordinator fees

The Groom and his family traditionally pay for:

• Groom’s and his parents’ attire
• Flowers, including all boutonnieres and corsages, bride's bouquet and going-away corsage
• Gift for the bride
• Bride's ring
• Gifts for his groomsmen
• Honeymoon expenses
• Lodging for his out-of-town attendants
• Marriage license
• Officiant's fee
• Lodging and transportation for groom's parents
• Rehearsal Dinner
• Bachelor dinner, if there is one

Bridesmaids and Groomsmen pay for:

• Their attire
• Travel costs
• Gift for bride or groom
• Wedding gift for couple
• Organize wedding shower(s)

Alternatives

This division of expenses is based on standard etiquette, which is sometimes considered out-dated. These are some suggestions for other options to divide the expenses:

• Split the wedding costs equally among the wedding couple and each set of parents.
  
• Contributing relatives pledge whatever amount they would like to/are able to contribute. The couple works within this budget, or covers any additional expenses themselves.
  
• Contributors select the items they would like to pay for. Perhaps the groom's parents would like to finance the photography and bar costs, while the bride's parents will pay for all other reception costs and the couple will take care of the ceremony fees.

Traditionally, the bride's family is considered the "host" of the wedding reception, and the groom's family hosts the rehearsal dinner. If you are breaking from this tradition, you may need to adjust accordingly, such as including the groom's parents’ names on the invitation if they are contributing significantly to the ceremony or reception costs.