Stand straight with your feet shoulder width apart, holding the dumbbells by your sides.
Start by bending your elbow and bring the weights up until your hands are approximately level with the middle of your chest. Then slowly extend the elbow back down to just before the starting position to keep constant tension. Your hands should remain in line with your shoulders on the way up and down. Keep your wrists aligned with your forearms throughout the movement. Repeat for the desired amount of repetitions.
Avoid using momentum from the body to bring the weight up or dropping on the way down without control.