Talents for Speed-Leveling (Warcraft 3 frozen throne)

Talents for Leveling

This should give you an idea of how you should choose your talents for best leveling purposes.
Talents, lvl 10-40(shadow tree). There's a great JavaScript talent calculator here:

http://www.wowhead.com/talent/?rZZxMLt0xRt

Now you have 'Spirit Tap' the best skill for leveling/grinding, with this you could kill mobs that are around your level range without even having downtime. (That means no mana drinking, if you use this talent right you could grind mobs for hours not drinking mana)
Note: When engaging an enemy always have the sheild up before you start attacking ( recast the sheild as soon as you ge the spiritbuff if possible)
And remember the wand is your friend, saves mana and does very nice damage, you should always check the action house for a better wand than your current, every few levels.
And now when you've reached 40, and have spent 31 points into the Shadow tree, its time to get some nice talents from the Discipline tree.

Talents, lvl 40-60(Discipline tree)
http://www.wowhead.com/talent/?rVMGshZZxMxt0xRt
(Notice that We've put the last point into Shadow Focus in the Shadow tree)

This specc is purely for Leveling, after you hit 60 we've got some other speccs for you.

PvP spec(the facemelter)
http://www.wowhead.com/talent/?rxMGoZZEMMtctRt
This is mainly for pvp but if you get some nice gear you could be doing damage instead of healing in Instances.

PvE spec(the healer)
http://www.wowhead.com/talent/?dxgus00oZfxLcc0qL
This is the healer build, it can look like many things 31/20/0, 18/33/0 etc, mess around with it see what fits you.