Curl the weight to the common sticking point, right around 90 degrees of flexion. Squeeze the dumbbells as hard as possible to create an irradiation stimulus and improve muscle fiber recruitment. Hold that squeeze for 15-20 seconds.
After the hold, perform curls for 8-12 reps, or to technical failure. This creates tons of metabolic stress, mechanical tension, and improves the mind-muscle connection to build bigger, stronger biceps. Do three to four sets twice a week.