Choose a logical time to conduct the lesson. Christmas, after Christmas or after the child's birthday is ideal, since it is normal to send multiple Christmas cards or thank-you notes during these times.
Set out a fun assortment of cards, colorful envelopes and postage stamps with animals, cartoon characters or other interesting subjects to pique the child's interest in sending letters.
Make or sign a card with the child and place it in an envelope.
Demonstrate how to address the envelope: write the recipient's name on the first line; the street number, street name and/or apartment number on the second line and the city, state and zip code on the third line.
Demonstrate how to write the return address in the upper left hand corner of the envelope. Follow the same template as in the last step: write your name on the first line; street number and name on the second line; then the city, state and zip on the third line.
Place a stamp in the upper right hand corner of the envelope. Explain to the child that the stamp isn't just a sticker -- the letter won't be sent unless the stamp has numbers on it showing the current postage rate.
Make or sign a second card and place it in an envelope.
Quiz the child on how to address the envelope. Ask, "What goes on this line?" or, "What goes in this corner?" When the child answers all questions correctly, let him or her address envelopes on his or her own, with your supervision. Gently correct any mistakes he or she makes.