As an FFXI player, one big adjustment I've had to make is targeting before activating a spell/ability (I used a lot of <stnpc> and <stpc> placeholders that don't apply here), and as such I spent my first week trying to figure out the most effective ways to target enemies and players.

Duuude007's covered pretty much all the bases already, but I'd like to throw this in mix as well - if you go to Character Config and check the "Target filters" tab, you'll see where you have a drop-down box on "Weapon Drawn" that's defaulted to "Enemies." If you change that to "Friends," you'll still be able to target and attack enemies using the L2/R2 + L1/R1 "tab" function and also target other players using the d-pad, whether they're in your party or not.