CHOICE FOR YOUR PC
NWN2 resembles the Baldurs Gate series in that you create a single character around which the story revolves, and recruit controllable NPC companions along the way. There are several considerations to account for when creating your PC. Follow this link for more details on my protagonist and the joinable characters.
Roles
A number of different joinable companions will become available to you throughout the game, and each one brings a little something different to a party. The key to a successful campaign is to have your party members work together as a team, to have their roles and abilities mesh together effectively. Here are some roles typical roles:
Tank - Somebody whos going to stand toe to toe in physical confrontations with the opposition. Ideally, the tank will not only be able to cut the monsters down to size, but will also interject himself between the monsters and a more vulnerable party member and survive the blows that follow.
Damage Dealer - Not necessarily a tank in the sense that you make that party member be first on the front lines to hold up the enemies. Rather, the role is one of swooping in from the flank after the position has settled and then dealing as much damage as possible. Packing a two-handed weapon without a shield means a clear choice to committing that character to a Damage Dealer role rather than a tanking role. Two-handed weapons allow 1.5x damage on each hit, and also take better advantage of the Power Attack feat when the damage bonus increases from +3 to +6. At the same time, such a character will be more vulnerable due to not having a shield armor class bonus and therefore will not be as suitable to a Tank role.
Archer - Somebody who can target an enemy from afar with missile weapons. Can be especially important when facing a spellcaster who's aiming spells at the party from a distance.
Healer - Somebody who not only heals the wounds of the party members, but also removes the various maledictions that can afflict her comrades.
Damage Caster - Somebody who torches, or debilitates, the opposition with spells - preferably from afar.
Buffer - Somebody who bolsters the partys defences, or combat abilities, with spells. In Dungeons and Dragons rules, classes that fill the Healer role also come with spells that fulfill the Buffer role.
De-Buffer - The opposite of the buffer, in the sense that it is a character who inflicts weaknesses and vulnerabilities on the enemy monsters, making them easier to kill. A more indirect path to victory in comparison to the Damage Caster.
Item Creator - With the implementation of feats like Craft Wondrous Items and skills like Craft Arms and Craft Armor, who in your party will create the magic items you desire?
Thief - Somebody who takes care of the traps and locked doors and chests and such.
Dont consider this list as exhaustive. It is simply meant to encourage you to think about what it is you want each of your characters to accomplish for the party.
According to the Situation
The great thing about NWN2 is that the availability of multiple companions who can join you at any time allows you to be flexible about your party configurations, allowing you to tailor your party to the situation at hand. Sometimes the situation changes from one dungeon to the next, which means one party configuration will work better in one dungeon but a different configuration will be more effective in a different area.
Another way to think about it is that you don't always have to have one of each role in your party. Sometimes having characters who can do the same kind of role can lead to a kind of overkill configuration that can really overwhelm your enemies, even if you left out a different role completely. For example, sometimes multiple party members can bring together different buffs that stack and mesh together, which can make the party practically invincible during a physical confrontation. Such a party can be really effective in situations where the monsters don't have much in the way of spellcasting, particularly dispelling magics that can do away with your buffs. As another example, having more than one damage caster can be really effective overkill, especially when the monsters lack good saving throws, elemental resistances, and spell resistance.
What follows is a brief description of the kinds of roles the joinable companions can play, and in what situations they are most effective in:
Khelgar - You could keep Khelgar as a straight Tank by leaving him as a Fighter. Turning him into a Monk will allow him to be a kind of hybrid Tank and Damage Dealer. Contrary to popular belief, you can get his armor class really high if you're creative, notwithstanding his lower Dexterity. Give him the right set of Gloves and, in combination with his Flurry of Blows ability, he can really crank out tremendous damage.
Neeshka - The obvious choice for Thief. Her sneak attack ability allows her to be a really effective Damage Dealer as long as she positions herself correctly and carefully. Keep in mind that she will be nowhere near as effective when faced with enemies that are immune to sneak attacks, like undead and golems and elementals.
Elanee - Elanee is a character who can do something of everything, but not as effectively at any one thing as other characters. She should be thought of as a character that is not relied on solely for a certain role, but as a versatile support character who can add some extra oomph according to different situations. For example, she can add extra damage casting to help accentuate Qara's use of offensive spells. She can provide healing to supplement what Zhjaeve brings. She can bring some unique buffs of her own. She can also be a fairly effective Damage Dealer when she uses her Wild Shape ability.
Qara - The best Damage Caster in the game, period. She really shines when she gets to wreak havoc on massive hordes of enemies all at once. In situations where the party is faced with singularly powerful foes, Qara can feel out of place.
Grobnar - Grobnar brings two cards to the party. One card is his set of Inspirations, each of which provides a different buff, allowing you to pick which one you want active according to the situation. The other card is his Curse Song, which is like a party-friendly damage spell and an enemy debuffer all at once. When Grobnar combines his Inspire Defense buff with a Curse Song on the enemies, it can heavily tip physical combat in favour of the party. It can get even worse when other party members activate different buffs. Grobnar can also provide some archery, but he'll never be anywhere near Bishop's level.
Casavir - The obvious standout for the Tank role, especially when he packs a good Warhammer and a good Shield together. He can activate his Divine Shield ability if he needs to hold up plenty of dangerous enemies that will surround him. He can activiate Divine Might for when he wants to pack extra damage behind his Warhammer.
Bishop - The best Archer in the game, hands down. He really shines when he uses his Many Shot and Rapid Shot abilities to wear down enemy spellcasters, or even kill them outright. He can also be an effective Damage Dealer when he seamlessly switches over to a two-handed weapon.
Shandra Jerro - There is, as with any other Fighter, more than one way you can go about developing Shandra. My preference is to put her Parry skill through the roof so that she becomes a highly effective Tank who occasionally counter-attacks while holding up the monsters.
Sand - Sand is often most effective when he uses his spells to buff his companions and de-buff the enemies. He's an ok damage caster, but no match for Qara in that regard.
Zhjaeve - A Healer and Buffer first and foremost.
The Construct - More of a Damage Dealer than a Tank. Armor class won't be as good as with other characters, but it has an insane Strength score and pretty much every feat that can enhance its damage (i.e. Creature Weapon) with its natural attacks.
Ammon Jerro - A Damage Caster, but with a different flavour than Qara. Qara can do more damage in a shorter period of time, but may be vulnerable if she runs out of spells (unlikely as that usually is). Ammon Jerro may take longer, but is a sure bet to wear everything down over the long haul. Will also be less vulnerable should enemies close in on him in comparison to Qara.
Building Your Knight-Captain
Ideally you should design your Knight-Captain to bring something the joinable companions won't, an avoidance of redundancy so that the Knight-Captain meshes well with whomever he or she brings on his adventures. Also ...
Flying Solo
There are certain points in the story where you have to go it alone, or at most with one or two companions. These solo situations can be pretty combat intensive as well. It behooves you to construct a PC that is durable and able to handle doing the lone wolf thing, even against multiple adversaries. You may want to think twice before deciding on a single class Rogue or Cleric. That is just my honest opinion though. Use your judgment.
A People Person
There are three people skills available in NWN2, Bluff, Diplomacy, and Intimidate. During certain dialogues, an option is available that is preceded by a skill name appearing within squared brackets. When you select that option, a skill check is performed. Success means that your skill level was enough to persuade the speaker to your benefit. You can finish the game without having to build up people skills for your PC. It is however desirable that your PC develop at least one or two of them. Keep in mind that only your PC can use those skills. A joinable companion won't be able to.
Prestige Classes
A number of Prestige classes are available in NWN2 which either provide unusual benefits beyond what is available to a single class character, or allow a character to blend together a composite of abilities from more than one class (much like 2nd edition multi-classing). Something to keep in mind is that with the exception of Khelgar none of the NPCs are open to changing their classes. Your PC is your one and only chance to avail yourself of a prestige class if thats what you want.
My Choices
Im including this simply for reference for how I proceeded with the rest of the game. My PC was Valeria, an Elven Arcane Trickster who also has thieving skills from three Rogue levels, as well as three Swashbuckler levels. My reasoning is as follows, a single class Rogue in my opinion has trouble hacking it during the later stages of the game, so I try to collapse arcane spell casting, melee combat ability, and thieving skills almost seamlessly into one character. Valeria is a very versatile character that's kind of a Damage Caster, a Buff, a De-Buffer, and a Thief all at once. Being such a versatile character also allows her flexibility to rotate her party membership depending on what kind of dungeon she's about to take on. The build is also done with foresight towards the Mask of the Betrayer expansion. As a good character, I don't want the abominable One of Many in my party (who could otherwise provide thieving skills). At the same time, I find myself underwhelmed by the thieving capabilities of Safiya's familiar, Khaji. Valeria, because she can handle both Thieving and arcane spell casting, will for the most part obviate the need to include Safiya in the party. Also, having the Insightful Strike ability from taking three levels in Swashbuckler allows her to add her Intelligence bonus modifier to her damage with her Rapier instead of her Strength score, which means she's no slouch in melee combat either.
My evil protagonist, Zarathos, was a Human Cleric / Blackguard. This particular build is also done in anticipation of Mask of Betrayer, because an evil Spirit Eater won't be able to tolerate the presence of the good aligned Cleric, Kaelyn the Dove.