I dont know if this is much of a neg, but when bored in the classroom and a chick keeps looking over at me ill mimik them.
she puts her hand up to her chin, i do the same. she realizes what shes doing and moves her arm down to the table, i do the same. Eventually she catches on and as i continue the game she starts giggling.
Then introductions or whatever are made afterward.
thats called mirroring. It is a way to make a girl more comfortable because you have the same mannerisms. Normally, when you go sarging, you don't want to be so overt about it, but in your situation it seems like a very good thing to start a conversation later. You could open it with a neg like "You were copying me all through class!" or "You put your arm in funny positions, (maybe use this part) its cute"