SETUP: Hold a dumbbell in each hand and stand upright (chest out & shoulders back). I like to get into a split-stance, as this provides greater stability against a heavier weight.
REP: Squeeze your biceps HARD as you curl the weights up, making sure to keep your elbows tight to your sides to avoid swinging them up. Keep your hands in a neutral-grip (palms facing in), as this will engage the long head of the biceps to a greater extent. Anything above 90 degrees is a good rep, but you should also control the negative phase (lowering the weights), as many of the benefits to this exercise are in this portion of the rep.
TIP: Ensure you lower the DBs all the way down, you should be able to flex your triceps at the bottom of every rep. We do this because the bottom half of each curl works our forearms, which is equally as important as hitting the long head of the biceps.