The easiest way to level in world of warcraft without buying a guide is using quest helper. Quest helper is a simple add on you can download and after you download it they will give you instructions on how to use it. But other than that you will log onto World of Warcraft and when you get quests you will see a arrow on your mini map that's flashing, this means that's where quest helper thinks you should go. So it is a simple process just follow the arrow and do what it says.
You can also bring up your main map and it will show you what it has planed what you are going to be doing where you will go and when you will be turning in quests. This is also very helpful because when you are in a group your add on will work with his quests to so you and who ever is in your group can quest together and not have worry about only doing what quests you have to get done.
Quest helper chooses the fastest root for questing, most of the time. It is a program and no program is perfect. So quest helper is the best way to level without having to pay for a guide. This is the most simplest way for questing in the game. Guides are better if you wish to train faster but for not paying quest helper is the best way. So now you can level faster than before with just a simple add on for World of Warcraft.