Wailing Caverns

The Wailing Caverns is a level 15-24 instance located in The Barrens just southwest of the Crossroads. The recommended character level for doing this instance is 18-24 but a lower level group can do fine fighting the monsters outside of the instance. This will prove to be a challenging and rewarding experience for new folks just starting out.

Quests

Here is a list of all Wailing Caverns related quests. Some of these quests have very good item rewards. The experience gained from completing all the quests is significant for characters up to their mid-20s.

Two quests are obtained in a cave just above the entrance to the instance, it can be tricky to make the jump to get inside. The cave above the entrance also has a leathercrafting vendor who sells two other deviate hide patterns. The three deviate hide recipes require deviate hides that are obtained in the instance and the pre-instance areas in the cave.
Deviate Hides
Rewards: Leather pants or 10 slot bag
Deviate Hides drop off just about any monster with Deviate in the name, it is usually easiest and fastest to do this on mobs outside of the instance in a small group (2-3).

Deviate Eradication Rewards: Mail gloves or wand or leathercrafting deviate belt pattern
The monsters for this quest are all inside the instance, unless you skip some monsters you shouldn't have any problem finishing this on one complete run.

Two quests are obtainable in Ratchet. As such, either Alliance or Horde may perform them. The rewards are XP and coin only.
Smart Drinks
These drop from any of the slimes you see inside or outside the instance. While doing some of the other outside the instance quests you will proboably finish this as well.

Trouble at the Docks
Mad Magglish is a stealthed goblin that patrols the cave outside of the instance. A few spots you can usually find him are:
In an alcove to the right shortly after entering the cave
After the shallow water section where you can go 3 ways, either down the left or right path
Also he could be walking between either of these locations or dead and waiting to respawn.

Two quests are obtained in Thunder Bluff.
Serpentbloom
Rewards: cloth gloves or cloth boots.

Leaders of the Fang Rewards: blue staff or a blue sword
This quest is a part of a quest line which begins having you explore the Oasis of the barrens and eventually sends you off to thunderbluff for this quest. It requires you to kill 4 of the major boss monsters in the zone.

There is one quest that begins from the last boss of the zone as well.
The Glowing Shard
Rewards: Talbar Mantle or Quagmire Galoshes