Mage Tips

Combat
Mages typically try and keep distance between themselves and their enemies. Although able to wield powerful offensive spells, they are particularly vulnerable to close range melee attacks. Spells such as Frost Nova and Blink are particularly useful to a mage when trying to keep their enemies at a safe distance.

Conjuration
Provide these conjured items to your party members when they need them. You might want to prepare some of this stuff before battle so you don't have to waste time inbetween fighting.

Conjure Food - Conjures X loaves of bread, providing the mage and their allies with something to eat.

Conjure Water - Conjures X bottles of water, providing the mage and their allies with something to drink.

Conjure Mana Stones - Conjures a Mana Agate, Citrine, Jade, or Ruby that can be used to instantly restore a significant amount of mana. Use them on yourself in emergency situations.

Profession Options
You can pick whatever you want. You might find these more tailored to the mage:

Tailoring - Tailors can create Cloth armor for themselves or sell it to others.
Enchanting - Enchanters can enchant their equipment to make themselves more powerful.
Herbalism and Alchemy - They can create buff potions or mana potions.
Player Submitted Information
Submitted by Unknown
Frost Nova, Polymorph, Blink, Blastwave, Cone of Cold, Counter Spell, rank 1 Arcane Explosion and rank 1 Blizzard are the most crucial spells for PVP. You should learn the timing and situations that each spell is most useful for. For example, if a rogue or warrior catches you off guard, your instant reaction should be Frost Nova, move away, and Polymorph. This gives you a window of opportunity to set up a series of spells. Cone of Cold is useful for rogues vanishing in front of you and also for quick turnarounds to slow down melee so you can get as far away as possible. Rank 1 Arcane explosion and rank 1 Blizzard are useful for searching for invisible players.

Submitted by Tacky, Drak'thul
In PvP, being able to kite (staying at range from a target for extended periods of time using slows and speed boosts) is one of a mage's more useful tricks. Although hunters are the true masters of kiting, mages have to learn how to kite as well because of their low survivability when engaging a melee class character. Different targets require different kiting methods. To kite a warrior or a rogue for example, you simply want to keep maximum distance to allow yourself the most time to maneuver, but against a hunter you would be wise to kite between 5 and 8 yards (the hunter's "dead zone"), because this allows you to avoid their ranged damage while at the same time staying just of reach of their melee capabilities.