That's a good question! Generally, you write something heartfelt and meaningful to the person receiving the card. It can be a personal message expressing your love, gratitude, and appreciation for the recipient. You can also share any special memories or moments you've had together, or include a few jokes and funny stories. Make sure the card is signed with your name and any other special messages you want to include. Most importantly, make sure the card comes from the heart and reflects your genuine feelings for the person receiving it.