This guide provides druid PvP tactics and tricks. If you're looking for a EXTREMELY in depth druid guide check out this, it covers everything you'll ever want to know about your druid.
Druid vs Warrior

Nature's Grasp, Starfire, Moonfire, Wrath, recast Root = Dead
Druid vs Rogue

Nature's Grasp, Faerie Fire, Starfire, Moonfire, Wrath, Recast Root = Dead. If they get out of root early, then slap a Regrowth + Rejuv combo on yourself ASAP and go bear form. Demoralizing Roar immediately, then stun them with Bash. Go back to caster. Root, and repeat.
Druid vs Mage

Sneeze in their general direction... Mages are so easy to kill with a druid it's not even funny. If you see Polymorph being cast, go into travel form (less mana cost) and you are immune. Keep Rejuv on at all times, and if you have Nature's Swiftness, then they are even easier. If you need to heal, do it a bit earlier than usual, and start a heal, then hit ESC to cancel it, Mage wastes counterspell on you and you are free to heal, or if the counterspell silences you, that's the reason you start the heal a bit earlier.
Druid vs Priest

Have a hard hitting 2H weapon, melee a lot, and also keep Moonfire on. When they fear you and use their little shadow spells, use Regrowth immediately, and be ready with an instant cast Healing Touch. It's simply a battle of attrition as most priests blow 3/4 of their mana trying to kill you quickly. Survive the initial onslaught and you own priests 9 times out of 10.
Druid vs Shaman

Once again, a battle of attrition. Melee them, toss on Moonfire, and keep yourself healed. Heal right after they Earthshock or Frost Shock you. If you have to heal while they have Earthshock ready, start casting Regrowth, then immediately hit ESC to cancel the spell. 9 times out of 10, the Shaman will waste Earthshock on you that way. Sure you take the damage (that's why you do this, when you are at about 50% health), but you then can recast your healing spells and they cant do anything about it. Windfury Weapon is a bit of a pain, but it's easy to get past. Bear Form + Demoralizing Roar takes some bite from it, as well as a stun, go back to caster and heal. I have never found Shamans to be hard to kill.
Druid vs Hunter

Ignore pet, either use Nature's Grasp to root it, or Hibernate it. If Hunter uses Viper Sting (Mana Drain Shot) Use Abolish Poison to cure it. Root the hunter, get in melee range, and take him down.
Druid vs Warlock

Nature's Grasp the pet, Moonfire the Warlock, and keep Rejuv on at all times, be ready with a fast Regrowth or instant cast Healing Touch. Warlocks aren't all that hard to beat. Although sometimes it will take forever, since all some know how to do is spam Fear.
Druid vs Druid

Battle of Attrition once again. I haven't lost to a druid ever since going to a Restoration build. Melee, Moonfire, keep Rejuv on yourself, and be ready with a timely Bear Form stun to prevent healing. I have a VERY high spirit, so I regen mana very quickly, and will out regen most anyone. I don't worry about being low on mana against druids. Rooting them while they are in caster form will make them use a form that will waste some mana, but smart druids use Travel Form which is all of 110 mana. So if you see him use Travel Form to break root, don't bother doing it again.
Druid vs Paladin

Still haven't been beaten by one yet. Keep Rejuv on at ALL times, have a good hard hitting melee weapon, and use Moonfire as well. If you get to 50%, use Regrowth and Rejuv combo. I say 50% because if the Pally has stun up, then you should be able to survive till stun wears off, to then cast another Regrowth. Once again its a battle of attrition, outlast the Paladin's mana, and you will win.