Too often I see people don't know in which order to CC mobs and what kill order should be. Here's my take on it. I'm a warrior tank.
After everything is marked, here's the priority for a good CC pull.
1) Rogue sap : this is happening first because rogues can't sap mobs that are in combat.
2) Hunter trap : 2nd because usually the hunter will launch a trap, easier to do on static targets.
3) Sheep/root/sleep/wyvern/seduce/shackle/fear/hex/bind/repentance (I probably forgot some but you get the idea).
4) Banish: I put that one last because the tank or any AOE can't break it so it doesn't matter where it is.
5) DPS skull
6) DPS any other non-CC add
----> now kill order for the CC'ed mobs.
8) Hex : because Hex cannot be re-applied to an already hexed target.
9) Root/Seduce/Fear/Sheep/Trap/Bind/Sleep: In any order but I tend to keep trap for last, depending on how good the player is at his CC job. more on that later.
A good pull:
On a pull with good players, I see the hunter in front right alongside mage, druid, shaman or whatever other CC class has a mark assigned.
If you're a mage/shaman or any class that has a 1.5s cast time for your CC, you HAVE to start casting as soon as you see the hunter trap being launched, not after it landed. This provides a nice pull where all CC'ed mobs stay basically at the spawn point with your CC on it.
The rest comes, the tank picks it up then you unload immidietely on the skull.
A good tank will change the skull mark at roughly 30% of a mob being killed to the next one he wants killed to give you time to select it when the previous one is dead. That way you don't lose precious cast time doing nothing/hitting the wrong mob.
As a CC class, you have to CC your mob away from the tank. If you don't, it will probably break because of the tank or other DPS. If that happens, it's really your fault, not the people you break it. There are exceptions
Also very important: A long pull lasts longer than the initial CC so when you can, re-apply your CC again, the tank/healer will love you for it.
Common symbols for CC and kill order:
Skull: Kill that 1st, no exception. Even if the tank wrongly put skull on an easy mob and left a very dangerous mob for later, you should still kill skull 1st, splitting DPS on different mobs will mean a longer time with mobs alive. Kill it asap.
Cross: This is usually the 2nd target to kill and is not CC'ed
Square: Hunter Trap.
Moon: Mage Sheep.
Now those I just mentionned are really common accross all servers I would say. Next are some that change, here are mine:
Star: Rogue Sap.
The most important thing is to clearly state at the start of each run which symbol is which unless you're in a guild run but this post is about pugging mainly. Remember that you don't know the people that group with you and they don't know you. As a tank that pugs a lot, it is my experience that most people I group with start the run with me 'afraid' It seems that there's a lot of bad tanks running around. I am also kinda afraid of the DPS in my group. What if they can't CC? With each group I learn about my teammates, I learn that this hunter is very good at CC. He re-applies his trap mid-pull and can instantly trap and wyvern on the pull without the mobs even twitching.
After a few pull you, as the tank(assuming you are marking and leading the group) will have to adjust your pulls depending on the players you are with. If the hunter can't trap, try to work the way he does it, don't yell it will mostly end up failing the whole run. Change your priority if the players in your group don't fit your usual priority system. Example the kickass warlock can seduce, fear and banish without breaking a sweat while the mage always sheep at the tank's feet(bad). Well change your priority, maybe even stop marking moon for sheep and let your warlock handle the CC while the mage just DPS.
I totally agree im a healer and last night some dumb prot pally thought he was tough with is 100k hp and just tried to steam roll the whole group... i just let him die. and i got kicked.. still confused!