1-10 any race starting area
11-20 Westfall (Near Stormwind)
21-30 Darkshire (East of Westfall)
31-35 Refuge Camp (North Stranglethorn Vale)
36-40 Booty Bay (South Stranglethorn Value)
41-50 Searing Gorge (Will need help)
51-55 Fel Wood (Near Night Elf Starting Point)
56-60 Winterpsring (North/East from Fel Wood)
61-65 Hellfire Pen (Outlands)
66-70 Nagrand (Outlands)
71-75 Valiance Keep/Borean Tundra (Northrend)
76-78 Zul Drak (Northrend)
78-79/80 Storm peaks (Northrend)
79/80 Ice Crown (Northrend)
WESTFALL
When first entering westfall pick up two quests, the first quest is the one the man gives for a pocket watch the second is from the women to get feed bags.
The first I will describe is the easiest for stealth characters. Straight behind the NPCs are the feed bags in the field. They respawn rather quickly by the time you get the 4th the first that you got will be respawned, you need a total of 8.
The second quest is a little more difficult for lower levels but still not extremely difficult. Go to the farm a little up the road and to the west. There will not be a direct road to it. But it's rather large. There will be a small house with a higher level NPC inside it along with a dresser. Inside the dresser is the pocket watch. When doing this quest with a group this will take quite awhile to respawn between 8-10 minutes.
After doing these two quests. Head for the major town in the center part of westfall. I forget the name I will add that at a later time. It has a big tower and a lumber mill. You will need to grab two quests here. I am going to write this as if you are not being power leveled.
The first quest will be to get 8 gnoll paws the second is 15 red bandanas.
The first is the easiest, when facing the saw mill go directly past it over the hill, which in directions is south. After going south you should see a small pond Stevands Pond or such and a campfire with gnolls around it. Make sure to loot them quickly as they are bugged most of the time. After killing eight of them. Start the second quest.
The second quest is to kill humanoids. Go to moonbrook which is beside the gnolls. Keep going south till you hit the road which won't be hard to see, because you should be directly beside it, after you get on the road follow it to the village, unless you are blind you should be able to see it without walking in any direction. Kill the

brotherhood bandits here, each one will drop a red bandana. After doing both of these quests turn run back to the saw mill/tower/town and turn them in. You should be around level 15-17.
The next place you need to run is a small house inbetween the two places you have done quest in westfall. There will be main robots between here. Its closer to the first set of quests, but since we are at the second set of them go north until you find it. It's near the road and pretty easy to spot. There will be a man outside a field of robots with the quest. TO kill 20 robots. Make sure to get the names right. This is a somewhat dificult quest for this level but easily doable by any race/class combo. After killing the robots in this field you can go south and a little west to find another field of them. After finishing this quest, you should be close to level 19-20.
At this point you should be able to move over to

wood, if not grind out a little more expierence/equiment until you feel comfortable. A level 18 should do fine if expierenced in played WoW at level 18, if you don't feel comfortable do some of the simpler gathering quests to get up to level 20 then enter

wood. Which is located to the east of westfall.