The wepeon requirements will list whether they are based on Strength, Finesse or Intelligence; each gets a bonus from the applicable attribute.
If you are using a spear, Warfare skills receive a bonus from Finesse, rather than Strength; it should say in the tooltip when the damage is based on the weapon (in the Special section).
Whaaat? So a mage can do Whirlwind with a staff and get Int bonus?
I have noticed the note in skill and book description, but I thought its a bug in the description.