Outline what you are doing to them now for us.
Wrose is right about needing to experiment to find what works for you. So, what hasn't been working to date?
Ozzys suggestion is what's been working for me lately. Adding close grip chins to both my arm and back days have helped tremendously, as has the fst7 set at the end of my serious weight.
Current bicep work for me:
Cg chins, 4 to fail
Bb curls, 4x6-8 heavy
Alternate curls, preachers, or alternate hammers 4x8-10 hypertrophy focused, strong contraction and slow
Ez bar reverse curl, 3x10
Fst7: either hammers, or preachers, depending on whether I did the hammers earlier or not. I've been messing with those middle sets every few weeks, but the overall workflow remains similar.
And bb curls and fst7 preachers at the end of back day.
Between that and my tricep work, I've put an inch and a half on my arms in 12 weeks. More importantly, my arms are not completely triceps dominant anymore. Bis were always a tricky muscle for me. Just have to roast those fuckers to balance them out.