Sado said:
Can any of you veteran wizards tell me how you decide which spells you want to prepare? How can you possibly know at the start of the day what spells you are going to need that day? Do you just squeak by the lower levels until you have enough slots to prepare a little of everything to cover all eventualities? Or do you just stick with certain kinds of spells and hope you get a chance to use them?
I suppose you are 1st level, right? Which spells do you already know?
At first level, I would absolutely not prepare Magic Missile or other attack spells. The damage is so low that you should rather attack with a crossbow (you aren't much behind yet in attack rolls compared to the other PCs) and use spells for (1) defense and (2) utility.
At this level, scrolls are very cheap (12.5 gp + 1 xp for 1st level scrolls) so you better scribe a few of them as soon as you have time & money for two purposes: first of all, you should scribe the sort of spells which are perfect for a situation which otherwise doesn't happen every day (e.g. if you know the spell Hold Portal, Comprehend Languages or Mount, it's not worth to spend a slot every day if they're going to be used only now and then); otherwise scribe spells which are always useful "just to have one more" when you're out of daily spells (such as an extra Shield or Mage Armor).
Then concentrate on preparing spells which you are almost sure you are going to use:
- defensive spells: unless you're absolutely sure today you're not going to fight, they're never wasted; in 3.5 Mage Armor is the total winner against Shield for a long time, and it's a spell I always prepare at low levels
- utility spells (out-of-combat): Unseen Servant is the most versatile and lasts an hour; Charm Person and Hypnotism can be used to get a help very often
- offensive spells: if you decide to use a slot for an offensive spell at this level, better have some good reason. Usually the reason is that the spell achieves a non-damaging result which helps the whole party beat the enemy, and possibly affects more creatures: Color Spray, Grease and Sleep are all quite effective at this level and can easily turn into insta-kill. Don't waste your slots in damaging spells as I said above, and neither in spells which just give some penalty, because the effect or the duration may be too limited for the moment.
Finally, some cantrips are much better than others

at least for some time: Mage Hand, Prestidigitation, Light / Dancing Lights, Ghost Sound, Daze. Forget about damage-dealing cantrips unless you have sneak attack.