how do you assist in this game?

i thought it was T, but that don't seem to work. any ideas?

If works if you hit "T" after u hear "I'm attacking soandso"

To call out a target, ctl + space (or maybe shift, can't remember for sure.)

It's CTRL-Space to call the tartget, when this happens a little target icon appears next to your name in the part window, then if anyone else in your presses T, they will target the 'called target'
works really well if you designate one member of the party to call the targets and the other members press T to aquire their targets because the whole party then focus fire on 1 mob/person at a time.