What happens next?

How to sign a yearbook
Consider whose book you're signing.
Are they a good friend, a best friend, or just someone you've seen around in the halls? Write your message accordingly. Be honest but nice.
For friends, write an inside joke or a memory you have together. You can also write a sweet message like " dear alexis, i had an awesome time getting to know you this year, you're a great person and an amazing friend.