If you're looking to become more efficient at leveling then there are some WoW leveling tips you'll want to bare in mind. These aren't earth shattering but they have helped me out when it comes to leveling in World of Warcraft and I know they'll be beneficial to you as well.
This article is based on leveling when solo-questing in World of Warcraft as opposed to dungeons and instances.
WoW Leveling Tip #1
Whenever clearing questing zones be sure to accept every available quest so that you can plan the best possible questing route. Quests can always be abandoned once accepted, so don't worry if you accept a quest that doesn't seem worth pursuing.
ALWAYS cross reference both your map to ensure the best possible questing route is being followed and your quests log to ensure you're aware of exactly what you should be doing once you arrive at your new quest.
WoW Leveling Tip #2
This probably should have been tip no #1, but before you log into the game ensure you have a game-plan! As you grow in experience you will start to develop daily routines and systems, but for newer players it's easy to wander around aimlessly for hours.
Stay focused and have a plan, this way you're less likely to get distracted by other aspects of the game.
WoW Leveling Tip #3
A mixture of solo-quests and mob grinding is the most commonly used strategy for leveling. We touched upon quests but grinding also requires some forward thinking. Not all enemies are created equally in WoW and it's only worth killing enemies of equal or higher level. One or two levels lower than you is acceptable but any lower than that and the XP rewarded is to low.
WoW Leveling Tip #4
Something I see all to often in WoW is players going it alone! Although the social and group aspect of World of Warcraft can be a little daunting at first, it's well worth joining a few guilds and interacting with other players.
This can provide untold benefit as you progress through the game and remember don't be afraid to ask for a little help from your fellow gamers!
WoW Leveling Tip #5
A slightly more involved technique for leveling is your classes talent build. The combination of talent builds available is vast and it's worth researching which talent builds are best suited for leveling the class you're playing.
For instance I have found the Demonology talent leveling build to be the most effective for the Warlock class. You're basically after talents which will speed up leveling in any way possible whether it be increased damage output for killing the mobs or perhaps a talent that speeds up your character somehow.
If you're serious about leveling characters quickly and are considering leveling a few alts then you're going to want to consider investing in a decent in-game leveling guide for WoW that has the best leveling routes pre-programmed and extras such as best suited talent builds.