Jace: He would pout and put his hand on your leg or waist. It got your attention most, if not all, the time.
Clary: She would hum. She'd start humming some random tune. Anything from the starwars theme tune to bad romance. Sometimes she would start singing some of it. Not loudly though.
Alec: If you were working he'd sit right next to you and put his chin on your shoulder. He would read whatever you were doing. Most of the time you paid attention after a few minutes but sometimes instantly and hide whatever you don't want him to read. *Cough smut cough*
Magnus: He would tap. He would drum his fingers off the table, tap a beat with his feet, tap you or anything involving tapping. You would get annoyed easily by this but learned to keep composure....for like 5 minutes. After you snapped he would fake pout and say sorry then kiss you.
Isabelle: She would kiss you. It didn't matter where; forehead, check, hand, lips or even neck. It got your attention 9 out of 10 times.
Simon: He grabs your hand. He just does it and expects attention, sometimes you ignore him to tease so he'll wrap his arm round your waist.
Maia: She would ask and if you didn't respond she would do a dramatic huff. She would then attack you with tiny kisses until you finally looked.
Jordan: He'll say your name over and over and over and over again until you finally turn to him in annoyance. Most of the times he'll just say 'hi' and peck your lips.
Camille: She would hug you. She would pull you close no matter what you were doing and snuggle in. She didn't care if it seemed clingy. It got your attention most of the time so she kept doing it.
Raphael: He'll follow you around and stare at you until you finally looked up. If you commented on his staring he would say he was 'admiring the masterpiece'.
Tessa: She would start throwing things at you. Not a lot or anything big. She's tear up bits of paper into tiny balls and throw them at you. Rubbers, bracelet, ring or even a water bottle sometimes. You could ignore the little things but when that water bottle came at you, you screamed. It never hurt, well much, but it would frighten you when it was a freakin water bottle.
Jem: He would "accidently" nudge you a lot. Hands brushing, shoulders bumping, anything that wasn't too obvious and annoy you.
Will: Whatever had your attention he would take. Reading a book, snatched out your hands. Writing, pen chucked across the room. Something he couldn't pick up, he'd put you over his shoulder. It was annoying sometimes but funny too.