I would like to read some suggestions about sorcerer's spell selection. I found a topic on another forum, where it was stated lvl 20 sorcerer has the following nomber of spells known:
5/5/4/4/4/3/3/3/3.

Here is my thoughts:
Lvl 1: Armor (for start), Magic Missile, Spook, Find Familiar, Shield.
Other candidates: Identify (my blade will do it), Chromatic Orb (in 4.2 was not so effective), Larloch's Minor Drain

Lvl 2: Glitterdust, Strength (as starter buff for melees), Mirror Image, Vocalize, Web
Other candidates: Knock (I will have thief, so I don’t need it), Resist Fear (my cleric can do this), Horror (same type as Glitterdust and that is better), Stinking Cloud (same type as Web, just my fighters can ignore Web with Free Action)

Lvl 3: Flame Arrow, Haste, Skull Trap, Remove Magic
Other candidates: Protection from Fire/Protection from Cold (yes, my priest will know them, but wizard version is much longer duration), Melf’s Minute Meteor, Fireball (I will have a staff which can cast this combined with Lightning Bolt)

Lvl 4: Emotion, Stoneskin, Greater Malison, Ray of Fragmentation
Other candidates: Improved Invisibility (I dislike it because I cannot heal or buff invis characters), Secret Word (SI: Abj. make these useless), Minor Sequencer (I have never used any minor seq in 4.2 run), Spirit Armor (good starter AC buff), Spider Spawn (good early summon)

Lvl 5: Breach, Sunfire, Lower Resistance, Hold Monster
Other candidates: Spell Shield/Spell Immunity (good defenses against dispels, but maybe backsitting mage doesn’t need them badly)

Lvl 6: Improved Haste, Protection from Magical Energy, Protection from Magic Weapons
Other candidates: Chain Lightning, True Sight (my thief can do this with Detect Illusion), Mislead, Tenser’s Transformation (elemental staffs will provide this), Death Spell (there are 2 helms with this spell), Contingency

Lvl 7: Ruby Ray of Reversal, Mordenkainen’s Sword, Delayed Blast Fireball
Other candidates: Protection from Elements, Spell Sequencer, Limited Wish

Lvl 8: Abi Dalzim, Improved Tenser’s Transformation, Spell Trigger
Other candidates: Incendiary Cloud, Protection from Energy

Lvl 9: Wish, Chain Contingency, Time Stop + epic spells
Other candidates: Spell Strike

Spell selection for sorcerers is to some considerable extent a matter of playing style. So, take what I will write below as mild suggestions rather than strong recommendations:

Cosidering your own list as a starting template:

lvl1: I would prefer Larloch's Minor Drain over Spook. You also can cast Find Familiar from a scroll. Also note that find familiar can only be cast by the protagonist.

lvl2: I would omit Glitterdust and would consider Melf's Acid Arrow (or even Blur) instead.

lvl3: I would prefer Vampiric Touch over Skull Trap.

I agree. Dump Find Familiar... you'll only cast it once the whole game.

Get Melf's Acid Arrow in your 2nd level slots... you may as well have one spell in that level that can hurt enemies. It's nice on trolls and spellcasters early on.

I really like Dispel Magic in the 3rd level. It's nice to have a "reset" button, and I don't buff my fighters too much.

Level 4 for me always includes Stoneskin, Minor Spell Sequencer, Spider Spawn, and Greater Malison. I usually love Improved Invisibility as my last slot. You won't use it often, but it can save your butt sometimes. Avoid the Emotion spells (and spells like it: Horror for example). Save or nothing spells suck, especially in ToB where all enemies will save 99% of the time.

Level 5: Get Spell Immunity in there, drop hold Monster.

Level 6: Contingency is a must have spell.

Well, greater malison + emotion is a very good sequencer. I also enjoy greater malison + ray of enfeeblement + feeblemindedness. If they save against it it's a pity, but if they don't save they're doomed.

Personally, I would only pick armor or shield, but not both. I would keep spook instead and remove find familiar for something else (like larloch for the possible interruption of casters).

As a caster I always seem to use melf's minute meteors... they just seem to hit everything.

I never played a sorcerer/ess so it's nice to get some hints to what to do with Imoen.

Thx for comments!
About Find Familiar and Armor/Shield: Good points. I will take Larloch instead of Find Familiar, but there is no good choice instead of Armor.
Melf's Acid Arrow: Yes, it is a good disrupting spell at start, but later I found it useless in 4.2. Similar situation with Glitterdust and Web. Good early start, useless later cause of spell defense, magic res, good saves.
Dispel Magic: yes, it is good. But I have found myself to cast Remove Magic much more in 4.2 run, and my blade can do that 1 Dispel Magic, when it is needed.
Emotion: I am in a trap with 4th lvl spells... Emotion is very good combo with Greater Malison and Spell Sequencer... It is deadly at early game, success very rare later, but with a trigger nothing to lose if I try it. I managed even Chromatic Demon down with Emotion in 4.2 run. I won't have full time mage in my grp, so no other caster for Emotion, and my blades lvl 4 slots will be filled with Stoneskins... And as I wrote, I had never casted Minor Sequencer in 4.2 run. Well, I found scroll a bit late, and after that there were no useful any 1st or 2nd lvl spells in important fights.
Hold Monster: Yes, maybe SI better. I found useful Hold Monster in Planar Prison (1st improved enemy there with SI and I hadn't got any RRR at that time, so Hold Monster was the only spell which helped me to win that fight) and at Chromatic Demon in WK. These are only 2 fights which I remember. So I don't know, SI is important also.
Contingecny: Hmm, very nasty situation... Yes it is very good. Imho Impr. Haste and PfME are must spells. Chain Lightning and Contingency would be also good. Maybe I can skip PfMW.

Hmmm, I have doubts about taking sorcerer without a full time mage, especially cause there are so many good lvl 4-5-6 spells. Maybe I will take simply a specialist mage. Or I will do a 6 man run instead of 5 man... And take a sorcerer and a mage... Well hard choices...

Indeed. I remember my testing sorcerer knew no damage-dealing spells above level 3 apart from the anti-golem spells... I picked a lot of magic defence spells (Minor Spell Turning, Spell Turning, Spell Immunity), which you might not want in the unmodded game. In IA though it's useful because enemy spellcasters will spend time trying to bring down your mage's defences rather than decimating the rest of your party (sometimes at least). I didn't bother with the likes of Emotion, Hold Monster etc. My Auramaster could do Emotion and I never even tried Hold.

I would strongly recommend you pick up PfMW even at the expense of Contingency. It was by far my sorcerer's most useful spell.

You will find a good number of Contingency scrolls to be used by your sorcerer during the game. I wouldn't choose it as a 6th level spell for my sorcerer.

Imoen already has a (more or less) optimized set of spells for IA.