Remember this nursery rhyme
One, two-- buckle my shoe. Three, four-- kick the door. Five, six-- pick up sticks. Seven, eight-- shut the gate
S1,2: ankle jerk
L3,4: knee jerk
C5,6: biceps and brachioradialis
C7,8: triceps
(Category: Anatomy Mnemonic, Neurology Mnemonic)