tyt - take your time
oic - oh, I see
ty - thank you
yw - you're welcome
lol - laughing out loud
lmao - laughing my ass off
rofl - rolling on the floor laughing
*g* - giggle
plz - please
k - ok(ay)
xo - a kss and hug
There are many more, those are the ones I can think of off the top of my head ;-)