Here, try this link for descriptions of NPCs.
http://www.planetbaldursgate.com/bg/encounters/npcs/
You'll want a balance of skills, inlcuding fighting, thieving, mage spellcasting and priest spellcasting (including healing).
I'm not sure how much knowledge you have about the game, but I'll assume it is relatively little rather than a lot...
As for what class to choose for your main character, every class can be played well so this really does ultimately boil down to a matter of personal preference. The game favors the pure fighter class--you can become very powerful as a plain old fighter. Dual classing is also an excellent option for thief, mage, and cleric because it gives you more powerful fighting skills than if you played a pure thief, mage, or cleric: you can start out as a fighter, gain several weapons proficiencies, and then dual class to the new class. Of course you have to start all the way at the bottom of the new class and won't get your initial class skills back until you reach one level higher in the new class than your level in the original class. Only humans can dual class.
Some of my favorite classes:
mage (if a specialist a Conjurer)
fighter-thief (I like dual class best, but an elven multiclass is also fun--you just won't be able to earn as many weapons profs)
dual class fighter-cleric
multiclass mage-cleric (half-elf only; here weapons profs don't really matter, so multiclass is probably better than dual class; although if you dual class I know you can specialize as a mage and I'm not sure if you can as a multiclass)