I hope it is not too late for this, but here are my two cents.
Keep in mind that most weapons in the game are a random drop (you can't influence what you get). Also be aware that the final boss in the game (IWD, I've never played the expansion sets) can be hit with magic weapons of +3 or better. Thus you will need some really good weapons in the final section of the game. The best non-random melee weapons in the game (meaning you always get them in any game) with enchantment of +3 or better include spears, axes, daggers, flails, long swords, maces, hammers. Avoid taking proficiencies in other melee weapon groups (especially in halberds and scimitars). Also, all characters should be proficient in ranged weapons from the very beginning.
In conclusion, I would say that axes, spers and long swords include the best weapons you can find in the game - Slayer (spear), Spear of Kerish, Axe of Caged Souls, Joril's Axe, The Celebrant's Blade (axe), Alamion (l. sword), L. Sword +3: Enforcer, Restored Blade of Aihonen (l. sword) and the great Pale Justice (paladin only).
Countrary to what GawainBS said, I would suggest you give your druid daggers and slings (but not clubs and scimitars, as there aren't many good weapons of these types in the game).
As for tactics, use ranged weapons a lot in the early stages of the game - they work miracles. Later in the game use the ranger/cleric as a meat shield as your other party members assist him with ranged weapons and spells. I can't tell you how to use your druid, as druid are inferior to clerics IMO and I tend to use fighter/druid multiclasses instead of single-classed druids.