Server Types.
Before you create your mage there are several things you must decide. The first is what type of server you want to play on. A normal or PVE server focuses on player versus enemy battles and dungeon raids. On this type of server you will be spending a great deal of time in parties as the main damage, conjuring up food, and crowd controlling with polymorph. Mages can almost always get a party and this is also the easiest server to solo on. So even if you aren't inclined towards group play you may want this one.
On a PVP server players focus on fighting with each other. It is somewhat harder to level up on this type of server since you are facing two types of enemies and you will often be ganked by the opposing side. This is more brutal and requires more coordination with other players so you don’t get overwhelmed. Mages are one of the more dificult classes to play in PVP due to their low survivability. When fighting they must focus not only on damage dealing but keeping as far away from the enemy as possible. There are several tricks you can use to do this and if you get them down you will do well. Even with these though, it is best for you to try and group as much as possible when leveling on this server.
Finally there is the Roleplay server. RP servers have either PVE or PVP mechanics, but while playing you must put yourself in your characters role. Mages have a wide range of different roles they can play. Mostly they will be an intellectual type, but their motivation can be almost anything you can imagine form the quirky gnome curious about arcane energies to the serious blood elf seeking vengeance.
It is important to choose your server carefully because you can’t move to a different type of server once your character has been created.
Race
With the release of the Burning Crusade Expansion pack there are now six races that can play mages. The differences in stats between them all are rather small, especially at high levels so generally you should pick

the one that is the most aesthetically pleasing. There are some racial abilities though that you should consider before making your choice.
Human
Perception
For twenty seconds your stealth detection is dramatically increased. Three minute cooldown.
This is only really useful when fighting rogues in duels and guarding flags and basses in PVP. Since we go down very fast if ambushed it can give you a little bit of extra survivability. But when grinding or in a party I never even had it on my action bar.
The Human Spirit
Increases your Spirit by 5%.
This is a nice passive buff. But it means that for every hundred spirit you have you’ll only get an extra five. Five spirit is equivalent to about one mana and health regenerated every two seconds. Mages do go through a lot of mana though, so anything is useful.
Diplomacy
You gain a 10% bonus anytime you gain reputation with an in game faction.
This is my favorite racial skill in the entire game. After level fifty a great deal of you time will be spent grinding faction. So this amounts to a ten percent reduction on the time you have to waste killing the same mobs over and over again.
Sword and Mace Specialization
+5 expertise to one handed and two handed swords and maces.
This is useless for us since we can't even use maces and our melee is terrible.
Overall a human makes a very good middle of the road mage. It has no great abilities that really make them stand out but they are far from the worst race.
Gnome
Escape Artist
Instantly breaks you free from a root or snare effect. 1 min 45 sec cooldown.

Right after silence effects, roots and snares are a mages worst nightmare. If you can't move to get away from your enemy, they will take you down in just a couple of hits. You will occasionally find yourself using this in PVE, but it is a real life saver in PVP. One

thing to keep in mind though is that our Blink spell will free us from any snares already, so you may only want to use this as a last resort.
Expansive Mind
Increases your intellect by 5%.
A very useful trait for mages. Extra intellect is always good and will increase your survivability and damage dealing, but only by a small amount.
Arcane Resistances
Increases arcane resistance by 10.
In all honesty this is one of the least useful resistance racial. Arcane damage is one of the rarest magic damages and only found in select fights.
Engineering Specialist
Increases engineering skill by 15.
This is only useful if you take up engineering and might save you some money, but it doesn't help or hurt a mage.
Overall a gnome is an excellent mage, especially in PVP. Not only because of Escape Artist, but because their small size makes them harder to see!
Draenei
Gift of the Naaru
Heals your target over 15 seconds. 1.5 second cast, 3 min cooldown.
A mage with a heal is a force to be reckoned with. This is invaluable when playing solo and you are in danger of dieing, or even if you want to avoid having to eat. The amount healed rises with your level and gains a portion of your gears +healing making it a very useful racial.
Inspiring Presence
Increases chance to hit with spells by 1% for you and all party members within thirty yards.
This is probably the best racial ability a Draenei has. It increases your DPS by reducing the number of times an enemy resists your spells and helps out your colleagues as well.
Gemcutting
Automatic + 5 skill to Gemcutting.
This is like the other crafting racial. They aren’t terribly useful and have no specific benefits to a particular class.
Shadow Resistance
Increases shadow resistance by 10

Resistance racials are mainly used for lore purposes and are never enough to save you. As it stands now shadow resistance is only useful in a few select fights in dungeons. It’s a nice bonus but don’t worry to much about it.
As it stands a Draenei is very formidable as a mage. Inspiring presence is a great group buff and GotN will help you when you are alone. If I had to rate them, I would say they are the best race to play as an Alliance mage, even if they do look weird.
Undead
Will of the Forsaken
Makes you immune to fear, sleep and charm effects for 5 seconds.
This is without a doubt the most powerful PVP racial. It will break you out of some of the most annoying PVP crowd controls and give you a five second window of invincibility to fight back. It's more geared towards melee fighters like warriors or rogues, but it is still very useful to a mage. In PVE though it is not nearly as useful.
Cannibalize
Regenerate 7% of your total health every two seconds for ten seconds. Must be near a humanoid or undead corpse.
A some what situational ability and not terribly useful to a mage because we can conjure our own bread to heal ourselves. It can be used in combat though, so if you Polymorph an opponent you will have a bit of time to regain some health.
Underwater Breathing
Underwater breath increased by 300% percent.
Another situational ability, but very useful when needed. There are several underwater quests and missions and having to resurface for air is really annoying.
Shadow Resistances
Increases shadow resistance by 10.
As I have said before, this is nice but won't save you.
Overall an undead is one of the best horde races to play as a mage, and maybe one of the best in the game. Their abilities lend them towards PVP, but they will still be able to get by in PVE. If you are very interested in PVP you should strongly consider this race.

Troll
Berserking
Increases attack and casting speed for 10 seconds. Speed is raised by 10% at full health, increasing as health is lost to a maximum bonus of 30%. Costs 7% of base mana.
An interesting racial that unfortunately has limited applications for a mage. A minor casting speed increase is very nice, but you won't get the full effect unless you are taking damage in the process. The mana cost is also rather prohibitive.
Beast Slaying
You cause 5% extra damage against beasts.
This is a very nice ability when leveling up. But you won't find it of much use in a group because there are so few instances with lots of beast class mobs. When you do run into them though, you will have more DPS than you friends.
Throwing Weapon Specialization
Increases chance to crit with throwing weapons by 1%.
Useless since we can't equip these.
Bow Specialization.
Increases chance to crit with bows by 1%.
Also useless since you can't equip these.
Overall a troll makes an average mage. There is nothing that directly helps you except Beserking, which is not terribly useful. If I had to rate them I would say they are currently the worst horde race to play as a mage, though definitely capable.
Blood Elf
Mana Tap
Reduces the targets mana by 50+your level and charges you with energy for ten min. Three charges can stack total.
It is nice to be able to reduce an opponents mana, but it will always be a rather small amount, especially at the highest levels. This ability may seem somewhat weak, but it is very strong when used with its partner, Arcane Torrent.
Arcane Torrent
Silences all enemies within eight yards for two seconds. For each charge of Mana Tap you have you will also gain 5+your level in mana.
This is a very useful ability for both PVE and PVP. In PVE you will be able to gain back a small amount of mana at a steady pace, and in PVP you will silence all those around you. The silence part is tricky though since you have to basically be right next to one of your opponents, which can put you in danger.

Arcane Affinity
Increases enchanting skill by 10.
Another crafting racial that is somewhat helpful, but not really important.
Magic Resistance
Increases your resistance to all schools of magic by 5.
This is something of a mixed bag. While you may be more rounded against magic than the other races, you will negate less damage then them. Not bad but nothing to seriously consider.
Overall a Blood Elf is a very powerful mage. It is something of a toss up between Undead and Blood Elf for best Horde mage.