It's important to confuse the muscles. Therefore, never follow the same routine for more than 2 weeks. Confuse your muscles further by using confusing equipment, like curling with a trap or safety bar, or curling in a squat or power rack. Don't worry, everyone else in the gym will know that you're trying to confuse the muscles and they won't mind.
Also, on the subject of curling, a good routine starts with curls and ends with curls. The rest is just filler (which should include at least one more set of curls).
No citizen has a right to be an amateur in the matter of physical training…what a disgrace it is for a man to grow old without ever seeing the beauty and strength of which his body is capable. – Socrates