1. Tension at all times - Typically you see moments of resting at the top and bottom of a bicep curl. This drastically decreases the damage caused. Squeeze hard at the top and yes, allow the arm to fall, but keep tensing as the bicep stretches out, no rest at the bottom. Curling your wrist back towards you will also help keep tension on as the weights lowered.
2. Angle of attack - Varying the width of your grip as you curl is very important. It means your able to hit multiple areas. Using your shoulders as a gauge, your 3 grips should be just inside shoulders, shoulder width, and just outside the shoulders. The latter requires good external shoulder rotation.
3. Hand Position - Well rounded biceps require both width and depth. This means you must curl with the hands in supinated and hammer grip positions to hit the various different heads of your bicep.
4. Failure, always - Limbs generally respond better to a greater number of sets, reps and hypertrophy techniques. Don’t neglect going heavy, but they must always be trained till complete failure. If you can touch your shoulder, you haven’t gone hard enough.
5. Supinated Pull Ups - That’s all.
All the best 💪🏼