I'm wondering what is the best level to dual class from Fighter. I heard that 3rd level was the best because you can get your Fighter abilities back faster and you can have three dots in a weapon skill. Is there any benefit to keep leveling in Fighter after that if I'm trying to make a beefier spellcaster or mage?

Also, what's so great about the Ranger/Cleric dual class? That class combo only allows Cleric weapons and defeats the point of having Ranger as a class to begin with. The only benefits I can see is a healer who can fight a little better and hates a certain kind of enemy. It's the same problem for Fighter/Druids too, can only use Druid weapons but at least it fixes the armor problem. What's the best weapon choice for a Druid? I'm guessing Daggers because those weapons seem to be the most common. I've yet to find any decent scimitars, clubs, or spears. Of course, the farthest I've gone in this game is the Yuan-Ti temple in Dragon's Eye, so I'm guessing there's more varied weapons later on?

The main benefits for dualclassing from fighter or ranger is that you can have 18/00 str and can specialize in weapons.
Clerics only get one attack per round, if you start as fighter or ranger and specialize in your weapon you you get a +1 to hit, +2 to damage and an extra half attack per round, in combination with 18/.. str even 2 warrior levels are enough to have your cleric do more than double damage. If you dual from ranger you get even an additional melee attack per round if you don't wear a shield.

Dualing after 2 fighter levels already yields big benefits, dualing after fighter level 3 is even better since you can have *** in a weapon. 7 fighter or ranger levels add an extra half attack per round. Since fighters or rangers get far more hitpoints than casters at the first 9 levels you also get extra hitpoints for each warrior level you take before dualing.

Best weapon choice for druid (besides slings) is scimitar, scimitar proficiency affects polar bear form and you can use a shield. You can buy lucky scimitars for little money from Conlan and will find one with better enchantment later. You can also find a great club and spear later in the game, daggers are also fine, staves are a little disappointing on teh long run.

I recommend dualing after level 3 (or even 2 if you dual from ranger), waiting longer yields more powerful characters on the long run but you'll want to be able to cast spells in the first chapter, you'll never experience the benefits of low level spells when you don't get them before you're supposed to be able to cast level 5+ spells.

From what I was reading yesterday over at GameBanshee is that this was more true of IWD straight but with HoW installed you only got the druid spell level you had reached as a ranger before dualing.

What wasn't clear though was if that was from simply having HoW installed or if you start a game in HoW rather than starting your game as a full IWD game.

First paragraph in this post but there is also another short thread about it.

That's correct. I hadn't meant to imply otherwise. I answered in a bit more detail in the other thread. I believe it's applies in the base IWD game if you have HoW installed, not just if you start HoW.