1. run a search for "party" in topic, you'll get a bundle of threads about evaluating diferent parties
2.
http://www.sorcerers.net/Games/IWD2/iwd2char.zip
this is an exellent guide into IWD2 classes.
3. once you have thought of a lineup, post it, and let people comment on every char...
other than that, go with Julian's recommendations. you can't really go wrong with classes / kits, as long as you maintain "build" stability of:
Tank (high HP, good saves / SR, high damage)
Divine caster / "enhancer" (cleric is way beter than druid here)
Rogue (traps & locks)
Arcane caster / "nuker" (both classes are good)
these can be of course combined. i also find these roles to be usefull:
Scout (high hide & move silently)
Sniper (ranged attacks)
Talker (high intelligence & charisma, diplomacy, bluff, intimidation)
Magekiller (good saves, many attacks / round, sneak attac)
Loremaster (knowledge: arcana, alchemy)
these can be combined, too.
my suggestion is to try to think of a COMBAT and NON-COMBAT role for each char, as these are the two modes your chars will be:
Sorcerer: talker & arcane spellcaster
Monk or 2-weilding fighter/rogue: scout & magekiller
Paladin: talker & tank
Ceric or bard or bard1/cleric: talker / identifier & divine caster
Rogue/Fighter4: rogue & sniper...
you get the picture!