-attack of opportunity will typically activate when an opponent crosses into the physical weapon range.
-the wizard will normally attack first because of higher speed/movement/initiative and the fact there is no armor penalty for wearing robes. for example my ranger always goes first
-character formations really depend on personal style and strategies. I typically use the T formation or the arrow head, with the warrior in front (if i know enemies are ahead and im willing to run right into them) or with the ranger first so his lucky find and perception (may not be relevant) are in full force and so i can be even lazier and not have to always switch to the one then back and so forth.
-but usually warrior first, mages on the side and archer in the rear (they have the longest range)
I hope this helps!
