Landmarks:

• T4: nipple
• C6: thumb, index finger
• C7: middle finger
• T10: umbilicus
• L3: knee
• S1: sole
• S5: anus

Mnemonics:

• C6: Make a 6 with thumb and forefinger [an OK symbol].
• Stand on S1, Sit on S5, L3s on your knees.