thme: My party is:

Human Paladin
Human Fighter (will be dual classed to Druid)
Human Ranger (will be dual classed to Cleric)
Elf Fighter (will be a fighter/ thief)
Human Mage
1/2 Elf Bard

For the Fighter/ Druid, Ranger/ Cleric and Fighter/ Thief, how do you decide how many levels of the other class to take and when do you take them? For the spellcasters, do you just go straight Druid or Cleric from level 3 on?

Many Thanks.

grogerson: I may be wrong, but I'm assuming IWD1, not the 3E IWD2.

Fighter/Druid and Ranger/Cleric I have a target of 9th level. Personal preference: they get an additional weapon point at that level as well as max hit dice. Otherwise I'd suggest 6th level.

As for the elf - sorry. Only humans can dual-class. Either start as a fighter/thief or straight thief since you don't have one in the party.

kmonster: You can't dualclass elves so replace this character with a fighter/thief multiclass.
Your party should work well even without any added bonuses from dualclassing, so there's no need to play big parts of the game without cleric or druid spells.

Warriors get extra proficiency points every 3 levels and an extra half attack at level 7. Level 9 allows fighters (not rangers) to get 5 stars in a weapon for an extra attack per round with this weapon.
I'd just dual at ranger at level 2-3 to cleric and the fighter at level 3 to druid. Eventually wait with dualing the ranger until level 7 or with dualing the druid until level 7 or 9, but dual at least one of them early, playing the early game without healer is painful.

thme: Thanks. If I dual the Druid at level 3, do I just keep going in just Druid levels, or do you alternate levels? The question applies to the Cleric/ Ranger.

Coelocanth: You can't alternate. Once you dual class you lose all the abilities of the first class until your second class is one level higher than the original class, and you can only ever level in the second class from the moment you choose to dual class. So your character will be levelling in Druid for good from the moment you choose to dual class.

grogerson: @thme - Unless you install a component from Icewind Dale Tweaks (from the Gibberlings 3 website) called "Loosen Item Restrictions for Multi and Dual Class Clerics and Druids" be careful where you place your proficiency points. Once a fighter or ranger duals, if the cleric or druid can't use the weapon the points are wasted.

thme: ...I know I am fine for the Fighter/ Druid, but may have to reroll the Ranger/ Cleric.