Hickory: Aw! That's cute.
FerociousBeast: Oh good lord, please let's leave Hickory alone, I'm starting to feel sorry for him.
Back on topic, I also am interested in first play through advice. Other than for role playing reasons, are there any compelling reasons not to dual class, or are the benefits to the various combinations too much to overlook? Human berserker, atm.
One compelling reason not to dual class: When you first dual class, you will lose your first class's abilities. For instance, if you dual class your berserker to mage, she will, for a while, be nothing but a low level mage with lots of HP. This means she will be rather useless until her mage level surpasses her berserker level.
One more thing: if you dual-class too late, you may reach the XP cap (your old class XP counts toward it, so be careful) before you regain your old class's abilities. Be careful about that.
Dual-classes are much more viable in Pools of Darkness because that game caps by level rather than XP and (unlike the Baldur's Gate series) implements racial level limits, making multi-class characters essentially unusable.