General Information

Creating your character is a matter of personal choice as to what type of character you want you play, but there are some things that should be noted.  If your character dies then you have to load up from the last saved game, usually resulting in lost game time. For this reason, it is harder to play a mage, thief or multiclass character due to their lower hitpoints.  Secondly, you don’t really need a thief - as Imoen will join your party in Chapter 1, and she is a good thief.
Multi-Class characters have skills of more than one class, but advance levels more slowly and suffer from lower hit points than other classes, and you must remember that the experience cap in BG is 89000, which results in 44500 exp for two classes, or 29666exp for three classes.  This will reduce the maximum level you can attain with these multi-class characters.
Humans can dual class, which is a very valuable skill. If you want to create you main character as a mage, then you can create a human fighter with a high strength and constitution, then dual-class to mage after attaining level three. Level three allows a fighter to gain Mastery in using a weapon - providing a +3 to hit and +3 to damage.

It has been announced that level limits for Demihumans will not be introduced in Baldur's Gate 2:Shadows of Amn.

 
Statistics

While any character can (theoretically) succeed in BG, there are certain things that will make a character better.  Firstly, all characters should have a high dexterity - as it will provide a bonus to your AC (resulting in you being hit less often) as well as a ranged THAC0 bonus. Other statistics are more subjective based on your class.

Strength: Vital for all classes, as it dictates carrying capacity. Vital for hand to hand fighters to have 18 (and good percentile if a warrior).

Constitution: Should be high to increase maximum HP. If non-warrior, then it should be 16, but 18 (or 19 if dwarf) for extra HP if warrior.

Intelligence: 18 for mages - otherwise can be lowered.  Supposedly affects pathfinding, but can be lowered if desired.

Wisdom: 18 for Clerics/Druids, to give bonus spells and no chance of spell failure. Supposedly affects pathfinding, but can be lowered if desired.

Charisma: Valuable if you want your character to lead the party(usually only warriors or perhaps clerics), as high charisma will reduce store prices and have benefits with some encounters.
 
 

Thieving Abilities

Stealth: In BG 100% always results in success, as there are no penalites applied to stealth in any situation. (Apart from a thief will always fail if trying to enter shadows when a hostile enemy is in their sight) 50% is enough, as boots of stealth and Shadow Armor can get your thief to 100%.

Find Traps: This is an extremely valuable skill, as there are a number of traps scattered through the game. A low find traps ability will result in your thief missing them, and your party will get seriously damaged just when they don’t want to in certain parts of the game.

Pick Pockets: While not the best skill that a thief has, this is useful in parts of the game.  Stealing items off storekeepers and grabbing items off people are handy, but not an essential or super valuable ability.

Open Locks: A very handy skill that allows you to open chests, drawers, cupboards, etc. Gold and items are usually held in such containers, and valuable magic items such as potions or wands are often hidden in such places. While it is possible to acquire the knock spell, it is much more simpler to just open them with a thief.
 
 

Alignment

Alignment does not have a huge bearing on the game, but it does increase/decrease the experience you get from doing certain things.  For example, returning a lost item to someone, (or performing a similar good deed) will usually result in more experience for a good aligned character than an evilly aligned character. Generally, it is better to pick a good aligned character - as they will gain more experience from being a hero, which is the whole point of the game.
 
 

Weapon Proficiencies

The best weapon proficiency depends largely on your character class and make-up of your party.  The magical weapons that can be acquired in the game is an important factor when deciding weapon proficiencies.(Checking the item list before you decide would be a good idea)
When playing a straight fighter, it is usually only worth progressing to 3 stars for proficiency in any particular weapon, as this gives +3 to hit, and +3 to damage. 4 and 5 stars only offer an extra +1 damage.  Therefore it is best to have a fighter specialised in two different weapon types up to three stars. (Attainable at level 6)  Start the fighter with 2 stars in these chosen weapon types and then add one to each as you gain levels 3 and 6.
Having a large sword proficiency is definitely suggested for two fighters, as there are two +2 large swords in the game. Having one fighter with bow or crossbow(missile weapons) proficiency is also suggested, as missile weapons are very powerful.
Clerics can become proficient with all three weapon types they can use in the game. There are several +1 spiked weapons, but the best weapon a cleric can obtain is a +2 warhammer.
Thieves usually have no need for blunt weapons, and are best when proficient in bow,  long sword and short sword. Bow should be one of the initial proficiencies, with either short sword or long sword obtained at level 4.
Mages are not suited to frontline combat, and as such missile weapon should probably be the first proficiency a mage has. Small sword is probably a better choice than blunt weapons for a second proficiency, but it is still wise to keep your mage slinging bullets at your enemies.
Multiclass characters usually follow the rules of the most powerful fighting class that they are part of. Multiclass clerics always follow cleric rules.
 

Specific Suggestions

Never become an ordinary mage - always become a specialist mage. Specialist mages only suffer the penalty of not being able to cast spells from one opposition school (or two if an invoker or transmuter), and get an extra spell per level.  The best specialist mage is probably a conjurer, who is unable to cast divination spells(which aren’t very good anyway) and an illusionist is also another good choice(only necromantic spells are disallowed).

Dwarven Fighter: If given high percentile strength, 19 constitution, 17 dexterity, even at the expense of other characteristics, this character will make a brilliant frontline fighter. Being able to increase his constitution to 20 later on in the game, giving the character regeneration is reason good enough to have such a character.

Human Fighter/Cleric: Progress to level 3 in fighter, then dual class to cleric, obtaining 3 stars in blunt weapon proficiency.  This character needs a lot of high scores, preferably 4 18’s (Str, Dex, Con, Wis), but is a very powerful character.

Human Fighter/Mage: Same as above but obtain 3 stars in either missile weapons or bow. This will allow your character to utilise these weapons with a decent THAC0, as well as spell casting ability, and also benefit from high hit points due to gaining 3 levels in the fighter class. Requires similarly high scores as above.

Gnome Fighter/Illusionist: Similar to the above situation, and are sometimes best at the rear of the party wielding a crossbow or bow. However, casting a mirror image or blur (or both) on themself then equipping their armour makes them a very effective front line fighter. If you acquire a robe of archimagi, this character becomes more manageable.

Multi-Class Fighter/Thief: While the NPC Coran is this class, it is still quite a valuable class to start.  Having fighting and thief abilities is extremely valuable; being able to quaff a potion of giant strength and then backstab is often the quickest way to kill someone.

Multi-Class Cleric/Mage: While not best suited in the front line, this character will be a strong element of a balanced party.  The combined offensive and defensive spells of both clerics and mages make this character extremely dangerous in a combat. Charming or holding enemy humans, this character can make fighters’ jobs a lot easier.
 

Characters to avoid
 

Fighter/Cleric/Mage or Fighter/Thief/Mage: These have very low hit points, and tend to be hard to manage because of this. They can only get to low levels comparable to other characters, and are difficult to manage.  Armor must be taken off before casting spells, but put back on before getting into close combat.  The cleric combination can only use blunt and spiked weapons and slings, seriously debilitating the fighter’s abilities.  Generally the skills that these classes could offer are offset by the experience cap and the fact that a party is comprised of six people - which is enough so that such characters are not needed.

Druid (either single or any combination): Druids have few advantages over clerics, in fact the only thing that there really is to like about druids is their shape change ability.  They cannot use many weapons, and their allowed armour is very small except when combined with another class.  Even with decent statistics, the character still suffers from problems.

Cleric/Thief: As far as I am aware, this character cannot backstab - which is one of the primary reasons for becoming a thief.  Without this ability, the thief side of things is severely impaired, and just because of this, it is not really worth the experience. Unless you are really hard up for a thief, a character like this should not be needed.
 

Bard: Bards can fight, pick pockets, cast some spells, and identify things. While this may sound good, it is still much like a Fighter/Thief/Mage.  The bard will have higher hit points, and will be able to identify stuff, but will not really be overly valuable. The bard song is about the equivalent of a chant spell - and it permanently ties up one of your characters.
 

Making a complete party in single player

NOTE: I would not recommend doing this before you have beaten BG normally in a single player game.  Managing your party is some of the fun to be had in single player.

Many people wish to play single player with a party of six character they create themselves.  Using multiplayer for this purpose is possible, but the game is less responsive and requires more system resources than a single player game.  A multiplayer party can be easily transferred into a single player game with no ill consequences.  Follow these easy steps:
1) Make sure your single player quick-save slot does not contain a vital saved game.
2) Start a multiplayer session: Usually selecting serial connection and then creating a game will allow you to start a game.
3) Create your party of six characters and start the game.
4) Once in the game, press q(or the quick save key if you have changed it) to quick-save the game.
5) Quit BG, and go to your BG directory(or folder) on your hard drive.
6) Go to the mpsave directory. There should be a directory called ‘00000001-Quick-Save’.
7) Move or copy this directory from the ‘mpsave’ directory in the BG directory to the ‘save’ directory in the BG directory.
8) Now you can go back into a single-player game and load up the quick-save slot, and you will be running a single-player game with your party of six created characters.