If I am sporting two fighers in my party I will invariably make one a two weapon fighter. In my first attempts I would rush to it as soon as possible. Now my approach is more measured. I'll get my primary weapon focus and weapon specialization first along with some other feats such as cleave or combat reflexes . Then I will start to build my offhand weapon. My offhand weapon will be "light" so as to reduce the to hit penalties to only -2 for each hand. I would have to acquire the namesake feat two weapon fighting of course. Weapon focus and specialization. More advanced feats would be the next phase. Improved critical for both weapons. Improved two weapon fighting and defense possibly. My favorite build is using a bastard sword for my primary hand and a short sword for my offhand. The bastard sword does good damage and the short sword is "light". I have used a different build with Fruella, whom I have turned into a two weapon monster. Masterwork cleaver in her primary hand and hand axe in her offhand. The two weapons actually use the same proficiency! This frees up many feat options. What combination or system do you prefer. Or do you favor the old sword and board? Perhaps one great weapon doing massive damage.