Consider a full elf or half elf. Remember, mages need Willpower to learn better spells, so try to start with as much WP as you can without reducing your STR or CON to nothing.
Decide whether you want to be a pure mage, or a battlemage. If the former, be sure to develop Charisma. For every 4 CHA, you gain an extra follower slot. It's important that pure mages keep enemies at a distance, and rely upon good followers to do the melee work. I like to have at least 3 followers. (Note that an Expert in Persuasion gains an additional follower slot.)
Also build up Intelligence. Every 4 INT gives you the ability to run one additional spell in the background (until you move on the overland map, or rest, or lose all your mana, and faint). Typically, I try to have 8 or 12 INT by midgame.
First spell you should learn is Harm. It packs good, solid power, and gets better the more spells you learn. I then recommend taking Elemental Fire three levels, and learning Fireflash. It's a great area spell. Finally, run up all the way in Temporal (Tempus Fugit is fantastic) and Conveyence (Teleport saves a lot of time).
When possible, run Agility of Fire in the background, to speed up travel. If you expect a battle, run Tempus Fugit. Keep plenty of fatigue potions handy.
Hope that helps.