Leveling in World of Warcraft can be very hard.
  Although some classes are easier to level, they all have one thing in common.
It becomes harder to level when your level is higher.
But is should be hard to level faster.
In this article I will show you some common made mistakes and how you can avoid them.
1.
) Quests Most people tend to take one quest at a time.
It will give you some experience points, but it is very inefficient.
Traveling back and forward to collect the reward and take another quest is time consuming.
You are way better of with taking all quests in a specific area.
Sometimes you will over look a quest, but at the end of the article I will provide you with means to prevent that.
2.
) Switching Most people tend to use 'Alt + Tab' to switch to read their favorite World Of Warcraft website or change  their music playlist.
In order to avoid this I recommend X-Fire.
It is a free gaming messenger and has also music plug-ins.
This way you will save a lot of time.
3.
) Wrong Areas The most often made mistake in World Of Warcraft leveling is grinding (training by killing monsters) at the wrong area.
This way you die to easy, have a hard time getting experience points or wasting gold.
Good area to train are very specific to what gear you have and which level you are.
Also, characters who use ranged weapons can better train at other areas then characters who don't use them.