Marking is the first step in changing into a fledgling.  Before someone is Marked, they begin to get sick in a way that resembles the common cold or the flu. Then a Tracker tracks them down, raises their finger to their forehead and says the incantation:

" [person's name]! Night has chosen thee; thy death will be thy birth. Night calls to thee, hearken to her sweet voice. Your destiny awaits you at the House of Night."

The person then feels pain in their forehead. They are then left with a unfilled cresent moon where they felt the pain. It seems that a person can now be Marked with either a sapphire blue or red color moon, as Shaylin Ruede was the first to be marked with red and was the first of Erik Night's.

If the fledgling doesn't get to a House of Night, specifically the adult vampyres, soon after being Marked, their sickness will worsen and they will die.

People who have been seen getting Marked