As for leveling your wizard, it doesn’t matter too much which leveling specialization (spec) you choose as they can all level quickly and easily. Not that any of them are WoW’s “forgotten child” or anything like that.
A leveling specialization primarily needs ability to deal damage, but it also needs some survivability and control of the opponent. In PvP, things lean much more towards the side of survivability and in PvE (i.e. Raids) they lean towards damage: first, last, and always.
Where you are leveling also matters. For all mage specs, if you’re leveling up in dungeons, perhaps with the random dungeon quest tool, then you can lean much more towards damage than otherwise and the fire and arcane specs will likely outshine Frost. here. If you’re leveling up PvP, well, you can’t help your team if you’re dead and Frost is (for now) the PvP specialization of choice.
For general leveling (quests, grinding, a dungeon or two), the Frost Mage specialization is probably the one most people would go for, as it is the most flexible. Frost can deal a lot of damage and also has a lot of control and survivability. Cold, Slow, and Frozen opponents don’t do much damage. A Frost Mage also gains talents that deal much higher damage compared to those same frozen opponents. Last but not least, Frost mages get a pet water elemental and that’s always useful.
Choosing talents while leveling up is pretty easy. Some talents save a bit of time from your spell casting and I recommend that you skip them and grab the talents that freeze and damage your opponents. When you reach the third talent tier, choose Icy Veins, Fingers of Frost, and a point on Improved Freeze.
A couple of levels later you will want to take all the talents from the ice barrier, especially if you are on a PvP server. A little extra survivability makes leveling up a lot easier at times, especially when things go wrong.
The Fire Mage specialization can deal even more damage, but it relies on movement to survive. If you think of a “glass cannon”, you are right. Fire is also heavily crit-dependent, so you’ll run into streaks of divine damage and then a dry spell where you’re on the run a lot.
Arcane mages are somewhere between the fire mage’s “total damage” and the frost mage’s control. Arcane specialization can also deal impressive damage and perhaps has better mana efficiency than the others.
People always wonder which statistics are the most important. For any magician, the answer is intelligence above all else, and the Int value increases as your level increases. Int is the new Spellpower and is listed in your mana pool and some critical rating. Strength, agility, and spirit are useless, while the amount of stamina you want will depend on your ability to survive. I suggest a lot of Stam at low levels, but it really depends on your skills.
Don’t worry too much about stats like Hit or Crit until the end of the game. Just opt for Int and let the other stats follow as you find them. If you find gear with gem plugs and you want to use the gems, then choose … Try the same thing with the enchantments you want to buy. Fire mages value Crit more than others, and all mages can use Hit and Haste (in that order). So if you’re looking for enchantments, you can use Int> Hit> Crit (for fire) or Haste (for others.)
While the min-max crowd might argue, my opinion is that you should play the wizard spec that feels good. If you’re a natural Burninator, then play the Fire spec, even if Frost is the “flavor of the month.” The same goes for Arcane, especially if you like a more “magical” feel than an elemental one. Develop just a little skill with whatever you choose and you’ll level up quickly and easily, regardless of the specs.