| Assuming you want 5 guys:
You'll want at least 1 or 2 front line fighters. My personal favorite combination is a fighter and a monk, but barbarians and paladins will work too, especially given the next recommendation...
You'll want somebody good at conversations, if you want to do the quests (they're often lame but can garner you some nice items in one or two places). I like to have a guy take 3 levels of rogue (that'll give you enough conversation skill points to max them out as high as you'll ever want them to be). This will also let you disarm traps and open locks for the rest of the game. I'll often bump his appraise skill as well, as this will get you better prices from the merchants. After 3 rogue levels, I go fighter from then on. (You'll want him to be human or somebody that's got fighter or rogue as a favored class, to avoid an XP penalty.) This often leaves me with 2 pure fighter types (one of whom can sneak attack for +2d6 when he flanks), plus a monk who can hold his own too. (The monk needs really good stats in at least 3 ability scores to be good, but if he does he'll rock.)
Beyond that a cleric is a must. I often take the good and sun domains, myself (god=Pelor). This is good for domain spells and for crafting items.
You'll also want one wizard or sorcerer. Wizards make better crafters, so that's what I do. (Elves are my peferred here, as they get extra dex for AC and touch attacks, and they get longbow proficiency for free, letting them hang back and be useful even when conserving spells.)
So, in short, a nice balanced party is:
1 fighter/barbarian/paladin
1 monk
1 rogue3+fighter from then on
1 cleric
1 wizard
That said, almost any party can work. This has a nice balance, but the game's not hard enough to really require that of you.  | 
Advice for balanced begginer party 
Ranger's Favored Enemies 
Linear Mode
