Okay here are my sorcerer guidelines:
1) At least one attack spell per level, but try to not have more than two.
2) Don't take too many fire spells! There are more fire-immune monsters as you get farther into the game, especially in ToB.
3) Look for spells which get better as you level up. Fireball is bad, for example, because it maxes out at 10th level (10d6). Skull trap has half the range but has no maximum damage---if you're 20th level it'll do 20d6 damage, and three of them in a sequencer will do 60d6.
4) Ignore spells which can be replicated with items. Cloudkill may rock, but it rocks just as much when it's from a wand. Similar thinking for Aganazar's Scorcher, Fireball, Monster Summoning II, Cone of Cold and Lightning Bolt, though the wand versions of those aren't precisely as effective as the spell versions. There's no reason to take the spell Strength: there are plenty of strength-increasing belts and potions. Haste is tricky---you will have two pairs of Boots of Speed by the end of SoA, and about a hundred in ToB :-D so the only things you'll care about hasting are summoned monsters. How often will you haste a horde of monsters? More than once per day? I doubt it.
5) If you're not soloing your sorcerer, count on having another mage around to cast some support spells. You don't need to select Friends or Knock or any other spell that deals with problems that will be there after you rest. Likewise True Seeing is a great spell, but your local cleric, inquisitor or druid can cast it just fine, too.
6) Take multi-purpose spells! Glitterdust == Blindness + See Invisible. Pierce Magic == Lower Resistance + Ruby Ray.
7) Project Image! This spell increases your firepower sixfold or more. It won't attack, though, so don't cast Melf's Minute Meteors with it.
Simulacrum sucks compared to this spell.
8) Don't ever take Protection from Fire, Cold, Electricity, etc.. That's what Clerics and scrolls are for.
-- Nifft