Grab a dumbbell with the right arm and place the upper arm on top of the preacher bench or the incline bench. The dumbbell should be held at shoulder length. This will be your starting position.
As you breathe in, slowly lower the dumbbell until your upper arm is extended and the biceps is fully stretched.
As you exhale, use the biceps to curl the weight up until your biceps is fully contracted and the dumbbell is at shoulder height. Again, remember that to ensure full contraction you need to bring that small finger higher than the thumb.
Squeeze the biceps hard for a second at the contracted position and repeat for the recommended amount of repetitions.
Switch arms and repeat the movement.
Variations: You can perform this exercise using a low pulley instead of a dumbbell. In this case you will need to position the bench in front of the pulley.
Alternative Exercises For One Arm Dumbbell Preacher Curl