MarthaStewart.com and InvitationConsultants.com are two online sources that outline proper RSVP formats for different occasions. Depending on the type of invitation, there are a number of options for RSVP wording.
RSVP is the commonly used abbreviation for the French phrase "respondez s'il vous plait," which translates as "please respond." RSVP wording can range from traditional to casual depending on the occasion. On a wedding invitation, the RSVP traditionally changes depending on the location of the nuptials.
There are several RSVP phrases that are universal across all manner of invitations, such as "The favor of your reply is requested before [date]."