What determines the special abilities you start out with? The ones listed in the F12 sub-menu. I made a male halfling swashbuckler and recreated him a couple times with different stats. Sometimes he'll get vampiric touch and can heal twice, sometimes he gets Horror and Murloch's Minor Drain and no vampiric touch abilities.

They are paired as such, and you get two casts/day for each tier (they don't have to be the same):
Good (Blue/Defensive) vs Evil (Red/Offensive):
Cure Light Wounds vs Larloch's Minor Drain
Slow Poison vs Horror
Draw Upon Holy Might vs Vampiric Touch

In BG1 you got them based on your reputation when resting after completing major parts of the game. If you start a new character in BG2 they are based on your alignment but, to my knowledge, semi-random.

The good abilities are way better with the exception of Horror and Slow Poison both being largely useless but situationally very powerful. Draw Upon Holy Might is an absurdly good spell to have at your disposal as most classes, and Cure Light Wounds is... less bad than Larloch's Minor Drain, since it gives a bit more healing every time you rest.

-- I'm rather surprised to see Sorcerer not only absent from the best PC list, but graded a B (with Blade at a B+!). It is unquestionably the most powerful non-dual/multiclass character, and in a party probably the most powerful player character choice period (although eclipsed by classes such as the Fighter/Mage, the Fighter/Thief, and the Fighter/Mage/Thief for solo runs). While I absolutely agree with the author that it is a terribly unfriendly class for newbies and I would not recommend it to anyone on their first run, neither are many of the classes and kits he loves like all of the aforementioned dual/multiclasses.

I consider Larloch's Minor Drain more useful than Cure Light Wounds, it's an instantly cast ranged spell which can disrupt casting, does damage and heals the caster.
For healing when resting you've clerics and druids, they get plenty of level 1 and higher level spells.
Horror is a powerful spell, but I never use it since I want my enemies staying close instead of running away.
Vampiric Touch is also very useful, you go to the enemy and suddenly deal 6-36 HP without a save and heal the same amount of HP.

The usefulness also depends on class, clerics get the "good" special abilities as spells while mages get the "evil" ones. Even Dsimpson isn't perfect, sorcerer is in fact the best class, far superior to normal mage. To get the same flexibility a mage would have to be able to memorize more than 5 times more spells than possible.
It's unrealistic to assume that players having their mage change their spells at every rest so they might cast more different spells with a sorcerer than with a mage.

It is a good class to play even for first time players, you get a familiar, there's no sorcerer NPC so this is your only choice for spontaneous casting which adds far more depth into the game then the stupid and user-unfriendly "know one night before what you're going to cast next day" metagaming. You choose the spells you like and then you're going to cast them a lot, you decide what you cast when you need it, not one day before.
Beginners might not always the most powerful spells per level (they wouldn't memorize those spells as mages either) but they'll definitely end up with some useful and fun spells for them at each level. In emergencies they can still cast spells from scrolls and chances are high that there'll also be at least one "normal" mage in the party (like the thief NPCs).

I suppose I'm slightly biased in that the good spells aren't strictly better, but Magic Missile is way, way better as a mage disruptor than larloch's and I can't think of any NPCs which use Shield (so anything that ignores MM should ignore larloch's at least as much, and often more so in cases like magic resistance and mirror image). In addition, except in the very early game it isn't actually a very effective damage spell so you should have more magic missiles than you know what to do with per day (unless you are soloing without any arcane casting classes).

RE Horror, I recently did a no-reloads run and since then have tried to play less risky in general and I find myself using it even though it is seriously flawed, as you mentioned. Sometimes it can save your ass, and sometimes it can make a fight both easy and not particularly more annoying (for example, Prebek's house if you're doing that at an extremely low level). Eh, but without mirror image or stoneskin it is very easy to be interrupted given that it's melee range and has a fairly long cast time, and more importantly it just isn't DUHM. That said, you make a good point that Clerics would far prefer the evil line. Hadn't thought about it that way and I guess that's a pretty good point; the type of people who don't use a guide (or extensive game knowledge from having beaten the game several times) to build a sorcerer are the same people who won't do any research on which spells are good and thus probably will have a weak mage anyways. Either way, I wouldn't really recommend a newbie play a mage either (and Edwin is better than any PC mage can possibly be regardless).

I never got interrupted using Vampiric Touch and the additional hitpoints you get last for 50 rounds (5 times as long as DUHM), my sorcerer once got drained to level 1 but he still had lots of HP since he used this special ability earlier.

I always had good luck going with Cavalier. To be honest, I know evil parties are supposed to be able to play through the game, but the quests and the story are really more targeted and good-aligned characters: the good resolution to most quests nets you the most exp, even if not the most gp.

Anyway, the cavalier: Just as good as a normal pally, but with some smoking hot bonuses. Plus, the restriction on missile weapons can be circumvented, if you need it to be, with thrown weapons: darts, knives, axes. Just give him azureedge and let the sparks fly. Plus, Carsomyr...

Maybe not the most interesting choice, but a great one for classically good party. It's worth noting with Keldorn, the 'best' outcome of his personal quest leads to him having to lead the party for good, as far as I can work out.

I agree with a lot that's already been said: Fighter, Paladin, Barbarian or Ranger is the way to go. I think many of their kits are very straight-forward too (but on the Fighter, avoid the Wizard Slayer and Kensai! Wizard-Slayer is an extremely difficult class to play, and Kensai is powerful but difficult to use).

I think my first BG2 char was an Archer, that was fun. Towards the end of the game it's not as powerful, but it'll get you through no problem, and being near the back means less frustrating re-loads.

You can figure out spellcasting easily through your party members, but Ranger and Paladin (except Inquisitor!) get some modest casting abilities and can help show you the ropes as well.

There is one thing I wanted to contradict from this thread, though: DO NOT NEGLECT WISDOM! If your WIS is below 7, on any character, you'll get penalties to resisting spell effects, and charm/disabling/death spells can be the quickest, most frustrating game-enders. The lower the chances of you falling prey to them, the better. I don't believe there's any difference between 7-12 WIS, so you can just keep it at 7. 13+ WIS actually gives resistance bonuses, but they're not significant enough to be worth putting that many points in unless you need WIS anyway (in which case they are rather nice). If you got a nice roll and have maxed out your important stats, then by all means, throw some extra WIS in. But don't go out of your way.

Also, I would say avoid dual-classing your first time through, since it requires some forethought and preparation, and the transition period can be difficult. Better to learn more about the game first.

Wisdom doesn't affect resistances at all, it was never implemented, just read the BG readme. If you want good saving throws use little races, they get huge bonuses.

kmonster is 100% correct. Wisdom save penalties against spells was never implemented.

Even if you tell him that you "release him from your service," you can still go back to his house a day later and recruit him again. At that point, you have the option to let him vanish for good, but he's willing to rejoin. Even if you let him go forever, you can still get him back in ToB. At the end of ToB, he retires to be with his family anyway, so you're only delaying it a few months. In general, I only feel moderately conflicted about using him.

I am new to BG2 and the AD&D too...kinda. I played NWN2 and that mask add on and a little bit of BG1 (never got too much into it), but that is so long ago, that i forgot everything about the system.

So i started BG2 and took forever to decide which class i take, decided I want to play the evil cleric version (Talos?) and after playing a little bit decided I'm going to reroll. I'm allready confused with all the spells of my teammates, so I will grab a Kensai and later dual it to thief, since i read that's a nice and easy combination (backstab with 2 swords and such stuff) and cause i don't want to deal with any more spells for my first game, even though I'm pretty interested in the magic system....but I'll leave it to my NPCs

You'll still have to deal with spells, it's just your party members that'll do the casting. But they're not on autopilot, you'll have to tell them where to aim those fireballs, dispells and buffs at.