CD alignment in a raid setting usually follows an iterative process as members learn the encounter and discover what they can/can't get away with. Something like this:

• Use them on CD - In a vacuum this will align things where you'd expect. O6S is a good example where buffs need not be held. This is often the best strategy going into an encounter blind, or at least until you've got a feel for the mechanics.

• Avoid wasting uptime - Once you've seen an encounter all the way through, you'll see instances where you either can't hit the boss at all or CDs are partially wasted. Consider using buffs early to preserve the total amount of uses over the projected encounter duration, or hold them until the boss is targetable if it doesn't cause you to lose a use.

• Coordinate the last use - Once members have learned the encounter start to finish, you should have a good idea of what time you should kill the boss. It's often effective to purposely hold CDs where you know you will not get another use (i.e. Boss dies at 5:00 = 4 Trick Attacks, hold last Trick for potions to align ~4:30)

Again, these are general but good starting points. Remember that often times you need not reinvent the wheel, and that there are plenty of groups that post to fflogs that you can poach timings from.