Do:

• Un-rack bar from pegs, then take two steps back
• Stand with feet shoulder-width apart
• Step backward into lunge position, keeping weight on front heel
• Lower until back knee is almost touching ground
• Drive forward into start position
• Perform 6-8 reps on each leg, with a 90-second rest between sets

Don't:

• Stay on toe of front foot during lunge
• Let front knee move over toes
• Hunch over; keep chest up and abs tight
• Step back with a stiff leg
• Perform more than 8 reps at once on each leg
• Use so much weight that it affects your technique