Alcamtar
Explorer
In the immortal words of Gary, from the 1E DMG:
"Never give a sucker an even break!"
Okay, so he was quoting someone else. Seriously, the whole point of all those rules in 3E is to master them and use them effectively. You don't give hints to your opponent in Chess, why do it in D&D? Doing it yourself is the whole point of the game.
(A related question is: do you allow them to kibbitz in combat? You know, pause for five minutes between each round and weigh various attack routines and coordinated maneuvers? Using out-of-character knowledge? If not, I wouldn't think you'd want to give hints either.)
If you want them to pay more attention to AOO, make the combats tougher. They'll start paying a lot more attention to tactics and rereading the rules and looking for anything that gives them an advantage.
In any case, as DM I find the players out-think me frequently, which isn't surprising considering I'm outnumbered. So if they make a mistake or play less effectively than they might, I figure it just evens things out a bit.
D&D is a game of escalation: levels, monsters, spells... If they aren't fighting at max potential now, that's okay. Personally I enjoy the lower levels when the team isn't as powerful and effective, because it lets me do things I couldn't do at high levels. So my recommendation is to enjoy it while it lasts -- once they get on the ball, the cat is out of the bag and there is no going back.
"Never give a sucker an even break!"

Okay, so he was quoting someone else. Seriously, the whole point of all those rules in 3E is to master them and use them effectively. You don't give hints to your opponent in Chess, why do it in D&D? Doing it yourself is the whole point of the game.
(A related question is: do you allow them to kibbitz in combat? You know, pause for five minutes between each round and weigh various attack routines and coordinated maneuvers? Using out-of-character knowledge? If not, I wouldn't think you'd want to give hints either.)
If you want them to pay more attention to AOO, make the combats tougher. They'll start paying a lot more attention to tactics and rereading the rules and looking for anything that gives them an advantage.
In any case, as DM I find the players out-think me frequently, which isn't surprising considering I'm outnumbered. So if they make a mistake or play less effectively than they might, I figure it just evens things out a bit.
D&D is a game of escalation: levels, monsters, spells... If they aren't fighting at max potential now, that's okay. Personally I enjoy the lower levels when the team isn't as powerful and effective, because it lets me do things I couldn't do at high levels. So my recommendation is to enjoy it while it lasts -- once they get on the ball, the cat is out of the bag and there is no going back.