1. **Outer Envelope**:
- Address the outer envelope formally with titles and last names. For example:
"Mr. and Mrs. John Smith"
"Dr. and Mrs. James Johnson"
- If the guests are unmarried or have different last names, list their names separately on separate lines:
"Ms. Jane Doe
Mr. John Smith"
- For families with children, you can include their names on the inner envelope:
"Mr. and Mrs. John Smith
Emily, Jacob, and Sarah"
2. **Inner Envelope**:
- Address the inner envelope more informally, using only the first names or nicknames:
"John and Jane"
"Sarah, Emily, and Jacob"
3. **Return Address**:
- Include your return address on the back flap of the outer envelope.
4. **RSVP Card**:
- Include an RSVP card with a pre-addressed, stamped envelope for guests to send their responses.
5. **Special Cases**:
- For guests with professional titles, use their appropriate titles (e.g., "Dr. James Johnson" or "Judge Jane Smith").
- If a guest is bringing a plus one, but you don't know the plus one's name, you can simply address the invitation to the main guest and add "and Guest" after their name.
Remember to check for any specific preferences or traditions in your family or culture. Ultimately, the most important thing is that your guests feel welcomed and appreciated!