The first movement I hold my upper arms out and frozen to the sides. This is by far one of my favorite bicep exercises. The trick here is to not let your upper arms drop at all. In fact, you should bring them out then up slightly, freezing them in position. This means there will be constant tension on your arms with zero breaks. You could actually hold the dumbbells out to the side without moving them and still get a great bicep bump. As I curl the dumbbells I resist the urge to drop my upper arms. I also do not curl all the way back as doing so would not ad any extra difficulty. Keeping the dumbbells further away from the torso increases difficulty.
The next two movements are simply lowering my upper arms to change the angle of attack. I’ve included them as they make excellent super sets. As my upper arms lower I increase the range that I curl the dumbbells up.