Remember that you must spend at least 50% of your total character points on magic-related skills, powers and talents, OR spend less than 20% of your total character points. The reason for this is to differentiate between actual wizards, and other characters who might have picked up a cantrip here or there.
Example: Blort the Obscene, the dreaded scourge of the steppes, is a horse-nomad warrior. He's not a wizard as such, though he knows a few very minor spells useful in his line of work — banditry and grave-robbing. Because his character is built on 75 points plus 75 points of Character Disadvantages (150 points in total), he can only spend a maximum of 30 points on magic. 3 points goes on a Magic Skill, another 6 points on 3 2-point Magic Skill Levels (to compensate in some measure for his rather limited intellect), 15 points go to build a small magical Multipower pool, and 6 points go on 6 1-point Ultra spell slots in the Multipower. That totals 30 character points, the maximum he can spend as a starting character. Of course, he can later spend points to improve his magical abilities as his adventuring career progresses, and he gains more character points through Experience.
Example: Blort's cousin, Krang, is a powerful tribal shaman. Like Blort, his character is built on a total of 150 Character Points. Krang must spend at least 75 points on magic-related skills, talents and powers.
INT is not included as part of your magic-related points spending, even though it is the characteristic on which the Magic Skill is based, so don't forget to take that into account when making your calculations.
In other words, do you wish to be a necromancer, an elementalist, an illusionist, a cabalist, a shaman, or whatever?
It is not strictly necessary to restrict yourself to a standard category of magical endeavour, but it makes it easier to create a coherent character conception if you do. Otherwise, it's all too easy to fall into the trap of creating a character who is nothing but a magical Swiss Army knife.
Where were you born? How old are you? Where did you receive your magical training? Are you married? What is your social station? These are the sorts of questions which should be answered when you're developing a well-rounded character conception, not just for wizards, but for any character.
If you have a home, or lair, or whatever, where is it? What is it? If you don't, why not?
This is obviously a fairly important question which needs to be answered when you're creating a new character. The answer could be very involved, or it could be as simple as "for the excitement".
It's not uncommon for wizards in literature to have an apprentice hanging about somewhere. If you do have one, it should be defined as a Follower if it has useful skills, or as a DNPC if it does not. The assistant need not be human, of course. It could just as easily be some sort of Familiar creature, or an imp, sprite or demon.
Some spells may require the presence of an assistant for the wizard to be able to cast them at all (see the Assistant Limitation)