Chachi,
I would also recommend isolating bis to their own day if you haven't already.
what I like to do:
1. alternating standing barbell 3x15
2. standing barbell 3x10 (I use a 2/3rds slow motion to isolate the muscle)
3. across the body standing barbell (not sure on the correct name for this one, but a trainer showed me it a while back and I've been hooked. Do one arm at a time, start with the weight positioned at your side and curl the weight across your chest. This will give you the definition on the side of the arm.)
I'm hesitant to do 4 biceps moves in a single day. I'll typically alternate weeks and rotate the standing barbell out with a standing preacher curl with my back against a wall. That really makes them burn!
I also like to punch the bags for 10-15 during a good cardio workout. That will tighten up the arms as well.
I've got fairly big arms using this system, relative to other areas of my body. The absolute key is isolation. The bicep is one of the most difficult muscles to isolate in my experience, in that other regions will try to help out such as the lower back. That is why I always do preacher curls with my back against a wall to completely isolate the muscle.
And I do this with fairly light weight. It's common for people to be worried about getting stared at for using light weight, particularly if you are a guy. But it isn't about the weight, and anyone that knows what they are doing understands this.