Setting it up
Your dungeon guide should probably be the one to set up the marks for crowd control. Alternatively, you should consider having your tank do so. Whoever sets up the marks should be the person who can recognize what the enemy mobs do and how the pull will go. It's just part of the overall strategy.
Obviously, make sure to designate which crowd control marker belongs to who and for which effect. For example, I'm accustomed to seeing the moon mean "sheep this."
As a very general rule, healers and tanks don't do a great deal of crowd control. That's because once the fight actually starts, they'll be exceedingly busy keeping everyone alive. The few seconds it takes to cast crowd control will take them away from that work and possibly lead to a wipe. That's not to say they shouldn't help crowd control when circumstances permit. As a general rule, they simply won't be able to CC.
Crowd control mid-fight
If you have crowd control, try and use it in the middle of each fight. Why not? It slows down incoming damage and helps everyone focus to such a degree that'll make the fight go faster. If your Polymorph runs out of time, re-cast it. If you have the ability to stun a mob, go for it. (Some tanks might ask you not to do that; I'm not one of them.)
There are millions of people who will tell you to eke out every point of damage you can or how to get your GearScore a little higher. However, what makes people absolute superstars isn't an extra 100 DPS. Who cares about that? What makes someone awesome is when he Silences that mob 20 paces away, forcing the mob to run into range of the tank. What makes someone awesome is when the healer's low on mana, so the rock star mage sheeps one of the mobs, lightening the healing load for the duration.
Anyone can do DPS. But the people who are fast and reliable on crowd control are the jedi masters of this game.
Interrupts, silences, and stuns
There are few fights that absolutely require that particular spells get interrupted. However, even those fights whose mechanics don't revolve around a single interrupted ability would be a great deal easier if everyone in the group uses their stuns, silences, and interrupts.
Using these abilities will cost you DPS. Do it anyway. Interrupt spells, stun mobs as they whirlwind, and issue silences when you can. If someone spams his or her damage meter in a party, respond with your interrupt meter.
There are some tanks who might ask you not to stun; this is because they need to position enemies in a certain way. That happens, and you should work with your tank. But at any given time, if you have the option to lessen the amount of damage your group is taking, why would you ignore it?
The CC options by class
- Army of the Dead Summons a bunch of ghouls to fight for the death knight. It isn't CC in a traditional sense, but in a pinch, it will lighten the damage load off the healer and tank.
- Chains of Ice Reduces a target's movement by 60% for 8 seconds. Great for delaying when a mob reaches the tank.
- Hungering Cold Traps all enemies around the death knight in blocks of ice for 10 seconds, but damage will break it. It's a great panic button but not as strong for an initial pull due to its short duration and long cooldown.
- Cyclone A very brief CC that keeps a target from moving, casting spells, or acting in any way. It doesn't last very long, but works great.
- Entangling Roots Holds a mob in place for 30 seconds but does not keep it from acting.
- Hibernate Puts an animal to sleep for 40 seconds; only works on beasts and dragonkin.
- Freezing Trap Traps a single target in a block of ice; can be broken by damage.
- Wyvern Sting Puts a target to sleep for a short time. Hunters do have to spec into survival to get this.
- Polymorph Turn your target into a critter for up to 1 minute. You can spam this ability over and over, but any damage to the target breaks it.
- Repentance Forces a target to sleep for up to 1 minute. Paladins must spec into retribution to get this talent.
- Mind Control The priest's player takes control of a target, making it an ally for a short term. This brings the side benefit of decreasing the number of mobs in a pack, since the other NPCs will instantly kill the mind control target.
- Shackle Undead Only works on -- you guessed it -- undead.
- Sap Renders the target unable to act for up to 1 minute.
- Bind Elemental Renders a target unable to act for up to 50 seconds; only works on elementals.
- Hex Turns the target into a frog for up to 1 minute; damage can break it.
- Banish Renders a target incapable of acting or being affected for up to 20 secondsl only works on demons and elementals.
- Fear The target runs around in fear for up to 20 seconds, unable to control its own actions.
- Seduction Prevents the target from taking any action for up to 20 seconds; actually cast by the warlock's Succubus.
Visit the WoW Rookie Guide for links to everything you need to get started as a new player, from how to control your character and camera angles when you're just starting out, to pulling together enough cash for mid-level expenses such as mounts, to dungeoneering and travel tips for lowbies.