Stand up and hold the barbell down in front of your with your arms relaxed and straight. Your grip should be wide (more than shoulder-width apart). This is your starting position.
Lift the barbell up as far as you can (as far as the natural range of motion allows you) and then lower it back down in front of you but don't fully extend your arms straight because you should always keep tension in your biceps (for maximum effect).
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 upper body or arms in an attempt to lift the barbell easier; 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 load the barbell with more plates.