I write the majority of this guide from a tank perspective, but please note this, speaking as a healer, just because you can survive a pull without cc'ing doesn't mean you should put that strain on your healer. If you can cc, please do. Your healer does not enjoy being low mana, especially if fecal meets rotary and they're on a sudden new pull with low mana.
You should always consider the CCs and their durations when figuring out your kill order. Glyphed saps for instance, are best left for last with the 2m, 20s duration. In non-levelcap instances, it's important to note that players may not be spec'd into the talents as early as possible.
1. Information on CCs & Tactics.
3. Comprehensive List of CCs.
5. Information on Interrupts & Tactics.
7. List of Interrupts.
1/25/11 - I've created a sort of in-game version of this guide, WhyNotCC, which can be downloaded at http://wow.curse.com/downloads/wow-addons/details/whynotcc.aspx, which covers the CC each type of mob can be controlled with and allows custom notes for each mob in the game. Screenshots @ curse.
CCs can break early. Some mobs while not immune are resistant to a particular cc or all cc and will break early, these can be re-applied but will have an even shorter duration because of the Diminishing Return and base resistance of the mob.
Some CCs (and interrupts) are talents. Every player might not be spec'd into them.
Disarms Rogues, warriors and Shadow Priests can disarm a target reducing damage output of the target. It's not CC but it is quite useful for helping the tank and the healer. Never be afraid to try to disarm either! Certain mobs that are immune to CC, such as the giant bone fellas in ICC are not immune to disarm and can do a great deal to ease the load on healers/tanks as well. Raid boss Gormok the Impaler in ToC was disarmable on regular mode. He would not impale his target for the duration of the disarm. Quite useful at the beginning and ending of his fight.
Diminishing Returns for CC only exist for the spell Cyclone and in PVE. No other non-stun spell suffers from DR.
Soothes These cause affectable targets to be less likely to attack.
Undead is not demon The few cc's that work solely on undead or solely on demons do not work on the other, please do not make that assumption.
Most Single target cc's can only be on one target at a time per player of that type. A warlock can't banish two targets, but 2 warlocks can.
Charms cause the player to take over the target and gain some of their abilities. While possessing their target, the player cannot control their own character. Healers should not MC and MC'ing is a consideration on movement sensitive fights.
Charms are affected by hit rating and distance. A player mc'ing a mob may wanted to be closer than their class typically allows.
You can, charm healer mobs and assist the healer in healing and negate the mob's own healing output on its friends. (Note that mc'ing another player only allows movement and melee auto-attack).
I also confirmed today, with the help of a lovely random priest, that casting Leap of Faith on a player who has charmed something breaks the Charm.
Many of the fears have useful glyphs now which cause the targets to cower rather than flee. Fear has often been dangerous to use as the mobs flee into 'friends'.
Most CCs will pull the mobs, so the tank should be ready to grab them. If you only need one CC, it's best to have someone besides the healer do it. Priests CCing should pop fade immediately after.
Unless otherwise marked, most CCs will break on damage taken. Many break immediately.. Some, like fears, have a tolerance for a certain amount of damage but may very well break on the first strike.
Transform forces the target to change form as a result of the caster's spell.
Sleeps and Incapacitates put the target in a harmless state. They stand there and watch their allies be attacked.
Most (all?) CC's can miss if the target is not properly hit capped. It is best to have a dps cc'ing as the tank may not, and the healer will not, be hit capped.
Horrors often function very similar to fears, the distinction is important. A mob resistant/immune to fear might still be horrified.
Spell categories are important because of the Diminishing Returns mechanic where when a target is spammed with a spell over a short duration (relative to the spell's base duration) the duration of the effect is reduced.