Stand up and hold the dumbbells down and to your sides in the "hammer" position.
Lift the dumbbells up all the way until your forearms are almost entirely vertical. Then, lower them back down but make sure you don't fully straighten your arms on the bottom portion because you should always keep tension in your biceps for maximum effectiveness.
Repeat entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Don't extended your arms completely on the downward portion of the movement
Don't swing your arms or upper body in an attempt to lift the dumbbells; this is cheating and does nothing for your biceps
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or use heavier dumbbells.