Because usually I just do 3-5 sets of Preacher Curls but I dont know if I should mix it up? Maybe do 3 sets of preachers, 3 of barbell curls? Also another question, is it okay to train biceps and triceps the same day?
Its perfectly fine to train Bis and tris in the same day.. As long as they are given sufficient rest before they are worked again.
I like to give my muscles 48 hours before working them again.. If i do a Back and Chest Session on monday night.. I Make sure i dont train either my biceps or triceps for another 48 hours.
As for the best bicep exercise.. Who knows.. Different things for different people... Currently im really digging an Incredibly hard Back session, followed by just a few sets of Negatives with the barbell or preacher curls!!