We pretty much frown on it in our group. IC is fine, but OOC isn't. We don't worry too much about using exactly the right "voice" for our advice, but the implication is that anything stated from one player to another translates to an in-character statement at an appropriate volume.
Somewhere in the PH, it says that you can only say about 6 words as a free action. We aren't Nazi's about this, but if a speech gets too long, the character is determined to have spent their action talking. Likewise, to keep things moving, players are only allowed about 20 seconds to start declaring their character's actions for the round.
And counting off squares isn't allowed for distances and once a figure is moved, the movement is spent. About the only time people get caught by AoOs is when they aren't paying attention, anyway.
Again, we aren't too strict on these rules. It just sets the baseline for play. Players are only called on them when the game starts to drag.
Advising is probably the strictest rule we have and it's a strict no-no OOC. The way around this is that we've recently implimented an anti-tangent system similar to Piratecat's, only it's XP rather than cash. If you want to advise someone, it counts as a tangent. Last session, I decided 80 XP was a fair price to advise the Cleric on how to best save our bacon when we were ambushed and badly wounded.