Write to someone who caught your eye β but make it about a moment, not a description.
The best notes aren't 'brown hair, always in the library.' They're the small thing that passed between you β a look, a laugh, the time you both grabbed the same door. Write it so they'll know it's them, and no one else needs to. That's the magic. Keep it kind and keep it anonymous: no names, no contact info, nothing that could let a stranger figure out exactly who they are. The mystery is the whole fun of it (and honestly, the vague ones land harder).