Note: This guide is not meant for power-leveling purposes. Rather, it is meant to show a player the most efficient way to complete all quests available for a particular zone. If you know of a better order or method to accomplish this, your input is welcome (in fact, greatly desired). For major changes, feel free to edit, but make a note in the talk page as to your reasoning.
Shadowglen is the starting zone for new night elves, and is located in north eastern part of Teldrassil. Other races may choose to quest here, but not all quests are available to them. If you are new to the game, check out the Newbie Guide to get started, or just dive in - the game has in-game hints and the opening quests are very straight-forward, just relax and have fun!
Begin killing Grell and Grellkin while moving towards the northwest corner of Shadowglen. Don't stop at the camps since there are plenty to kill along the way to our destination: Iverron, the objective of  A Good Friend.
Move northeast around the trees and hug Aldrassil, the big center tree, as you collect Hyacinth Mushrooms near the bases of the other trees. Look around. The mushrooms are usually in the nooks made by the smaller trees and bushes.
The timberlings who drop the seeds and the Timberling Sprouts are all along the northern half of the lake, and Fel Cones can be found in the same area. Once you have the required number of each, return to Denalan and turn in the two Timberling quests.
The next two quests are not connected or even in the same area, but should be done at this time for leveling purposes. Both  Twisted Hatred and  Ferocitas the Dream Eater can be a pain, so bringing a friend along is helpful.
Once you have found a [Shaman Voodoo Charm] from one of the furbolg shamans, return to Oben Rageclaw to receive the next quest,  Druid of the Claw. Note that some people skip this quest since it often takes a long time to find the voodoo charm.
Locate the druid's body at the bottom of the barrow den and kill it, then use the charm. Return to Oben for a reward.
Just southeast of the big lake is the moonwell you need for  Crown of the Earth (4). Right click your phial to fill it.
Go as far to the southwest as you can. Along the way you should see the Strange Fruited Plant, which looks like a giant tree with a pink glow around it. Right click it to receive the quest  The Glowing Fruit.
Warriors on the quest  Vorlus Vilehoof should now head towards the eastern side of the hills where the Ban'ethil Barrow Den is. You will find a path heading up into the hills, which will eventually lead to the moonwell and the satyr, Vorlus Vilehoof, whom you are after. Defeat him to complete your quest.
Return to Dolanaar and turn in the quests (Warriors head to Darnassus to turn in yours).
There are a lot of quests in the Oracle glade, and it is most efficient to do them all at once. However, make sure you prepare properly, or you may need to make multiple trips back to civilization for supplies.
Find Mist, the nightsaber, in the farthest northwestern point of the island. Talk to her to receive  Mist. You will need to escort her back to the Oracle Tree (where the Sentinel and moonwell are). Kill harpies for the  The Enchanted Glade quest as you go.
On either side of the farthest north point of the river roams Lady Sathrah, the objective of  Tears of the Moon. Defeat her and take her spinnerets.
West of this point (directly north of the Oracle Tree), rogues can find Sethir the Ancient for their quest  Destiny Calls. Don't attack him: though you can get the item in this way, he spawns several minions which make him incredibly difficult to defeat for this level. Instead, pickpocket the journal from him to complete the quest.
Head back south, picking up any more tumors you need from the timberlings in the river. When you have completed everything, return to Darnassus.
Go down to the lake and talk to Denalan. You should have quite a few quests to turn in, but be sure to turn them in one at a time: each time you turn one in, Denalan will plant something in his planter and a mob will spawn.
After all this Denalan should offer you [9G] Oakenscowl. This is a group quest to kill a named timberling in a cave just south of the lake. Grab a friend and head down there, defeat the creature, and return to Denalan.