As a new player, I'm finding the /who all command to be the most useful and powerful tool for finding groups and saving time. Some are obvious, some not so much! Happy Hunting!
EDIT: THANKS PICO for providing this link!
http://www.eqemulator.net/wiki/wikka.php?wakka=ZoneList
Using the Command: I'll use myself, a 21 bard named Sarem, and the zone Greater Faydark, as examples of the different things you can do with it.
/who gfay all
/who bard gfay all
/who 21 gfay all
/who Sarem all
/who bard all
/who 21 all
/who 21 bard all
etc.