Traditionally the bride’s parents are the hosts, but nowadays anything goes.
If the bride’s parents are paying for the bulk of the wedding costs, include their names on the invitation. For example, “Mr. and Mrs. Jim Conrad request the pleasure of your company at the marriage of their daughter Lauren Katherine to William Tell…”
When is it Happening?
Tradition dictates that you should spell out numbers in the date, like, “on Saturday, the second of June, two thousand and twelve.”
Addressing Your Invitations
The names of married couples belong on one line, unless they won’t fit. The names of unmarried couples belong on two separate lines, and always spell out “street,” “avenue,” “apartment,” etc. If you’re giving someone a plus one, try your best to find out the name of their guest and include it on the envelope.
A Few More Things
The line-breaks on an invitation act as punctuation, so there’s no need for commas or periods. Only proper nouns and the first word of a line that stands alone need to be capitalized.