General abilities
All druids regardless of spec have access to the most powerful crowd control spell in the game, Cyclone. Unlike other forms of crowd control, it can be cast on any target regardless of type. It's so powerful that not even a paladin's vaunted bubble or a priest's Mass Dispel can break it. The only way to remove it is through the PvP trinket, making it one of the select spells worth using the item for. Cyclone also has no cooldown, making it spammable on a target. This means that a druid can effectively take an opponent out of play for a long time, even with diminishing returns. Sometimes, druids chain cyclone different targets to sidestep this limitation. When an opponent is Cycloned, druids can cast heals on themselves, assault another target, or flee.

Druids are also able to keep opponents in place with Entangling Roots, made even more powerful in Wrath by removing the original "only usable while outdoors" restriction. It is also spammable but likewise subject to diminishing returns. This spell is used to establish distance and is sometimes triggered by Nature's Grasp, often activated by druids who need to escape from a melee opponent. In combination with their fast-moving forms, druids can establish a lot of space between themselves and an immobilized enemy. They can even use Hibernate against Hunter pets or opposing druids.

When fighting a druid, be prepared to be ensnared and crowd controlled. After using Cyclone, many druids will cast a long cast spell such as several heals or a massive Starfire, timing it such that the spell hits just as Cyclone breaks. This means players should be wary and be on the defensive after such spells. While druids have a plethora of offensive abilities, their means of using them varies according to form. Moonkin will kite and keep as much distance as possible (moonkin form doesn't confer too much protection) while firing laser beams and feral druids will keep enemies in place with a bevy of snares and stuns while tearing them to shreds. Restoration druids, of course, work primarily as support, keeping their more offensive-minded friends up... which probably makes them the most dangerous druids of all.

Speaking of restoration, as much as druids have different approaches, it should be noted that all druids are capable of healing themselves, albeit sometimes needing to change forms to do so. This makes them extremely difficult to take down, with even the rogue-like cats healing themselves reasonably well. One important distinction with this is that for obvious reasons, druids not specced into Restoration will have weaker and more expensive heals. Another thing is to remember is that druid healing consists of powerful heal-over-time components. This makes abilities such as Purge or Dispel Magic invaluable when fighting them. Keep those HoTs off! Most druids will have a HoT or two ticking on themselves to mitigate damage. Classes able to remove or neutralize these have a powerful weapon against druids.

Balance druids
Although a DPS tree, balance or moonkin druids suffer some disadvantages when engaged in melee and the Moonkin Form is mostly used for its offensive punch. This is why many Balance druids will open stealthily, casting a long, high-crit Starfire from a distance. It isn't uncommon for Night Elves to start Shadowmelded while casting a high powered nuke. Starfire and Moonfire are a moonkin druid's bread and butter along with Wrath, spammed from a distance and causing tremendous damage when left uninterrupted.

A balance druid is all about dealing damage. A whole lot of it. They will throw spells like Insect Swarm and Moonfire to apply damage-over-time effects and to boost their subsequent attacks, so classes able to remove debuffs should always make sure these stay off. The best way to deal with balance druids is to close the distance while they are in moonkin form. They will use Entangling Roots and Cyclone liberally, being the spec that is most reliant on them to establish proper distance and positioning. Catching them as moonkins means they will be unable to heal themselves and will be forced to change to humanoid form when low on life. This usually means they're in the worst shape, so take advantage.

Balance druids also have access to Force of Nature, which summons three treants to fight for them. These can dish out a lot of damage and push back spellcasting, which can be difficult for spellcasters. Smart Druids will also debuff opponents with Faerie Fire, allowing the treants to hit for a little more. While these minions probably won't kill a player by themselves, it buys the balance druid precious casting time, allowing them to fire off a big nuke to finish off opponents softened up by a mob of furious trees. AoE fears work well here, such as Howl of Terror or Psychic Scream. The idea is to get rid of the treants quickly and prevent the moonkin from doing more serious damage.

Feral druids
A melee druid is a fearsome opponent. Think of them as taking the best parts of warriors and rogues with the unparalleled ability to move around. In PvP, it will be more common to find cat druids than bears, whose abilities are generally geared towards PvE tanking. It isn't uncommon, however, to see druids shift into bear form in order to use Bash to stun an opponent or interrupt a spell. Out of three specs, feral druids benefit the most from stealthed openers, usually engaging their opponents with a Ravage or Pounce.

Cat druids can unload a whole lot of damage in a short amount of time, all while their opponents are stunned. They are effectively rogues -- with several abilities that mirror the class -- and can prove to be a handful for many casters. Most of their abilities and debuffs are also physical, making them almost impossible to remove. As mentioned, druids can heal themselves, giving them a slight edge against actual rogues in this regard. Well-timed Maims and Bashes not only interrupt spellcasting but are also used as a precursor to self-heals, so watch out for them. Be prepared to break stuns at strategic moments and not just at the first opportunity.

One key here is that cat form confers very little by way of protection. Cat druids can dish out a lot of damage but also take it in equal measure. Veteran druids will more often face melee opponents in bear form for the mitigation, switching to cat form only during stuns or when attacking from behind and the opponent is busy elsewhere. On the other hand, feral druids will often stay in cat form against casters because physical mitigation is useless, anyway. The idea is to deal as much damage to them when they lapse into cat form and prevent them from casting self-heals, which they'll preempt with a stun, Cyclone, or even Barkskin.

A good tip to remember is that while druids can break most movement-impairing effects, it costs a lot of mana. Because feral druids have low mana pools, they will avoid doing this too often. If you can spam crowd control or snares to force them to use up their mana shapeshifting. It's better than allowing them to spend their mana on heals, which is what they are saving it for. Feral Druids depend on Innervate to replenish their small mana pool, so don't allow it if your class can manage to remove buffs.