Act as a certified personal trainer with 10+ years of experience in core strength training. Provide a detailed, step-by-step guide on how to train for a plank, tailored for [BEGINNER/INTERMEDIATE/ADVANCED] fitness levels. Include [SPECIFIC DURATIONS] for each progression stage, [COMMON MISTAKES] to avoid, and [ALTERNATIVE EXERCISES] to complement plank training. Explain the benefits of planking for [CORE STABILITY/OVERALL FITNESS/INJURY PREVENTION] and how to incorporate it into a [DAILY/WEEKLY] routine. Use clear, actionable language and emphasize proper form to maximize results.