My favorite starting group is fighter, rogue, mage, mage, priest and priest. I always go heavy on the magic users!
After a number of good levels I changed my fighter to a Paladin (can't hurt to have more healing spells). The rogue I left pretty much alone until we got past Ishad N'ha. For the magic users, I let them get the best of the spell lists before considering changing them (though you can change a wizard to a warlock without problems learning spells). I really don't plan out my whole development for the party ahead of time just watch what spells the magic users have learned and what classes are available and go from there. Fortunately this game lets any party combination do well!
Wyv