Act as a certified personal trainer with 10+ years of experience specializing in shoulder development. Provide a detailed list of the [NUMBER] best exercises for targeting the deltoid muscles, broken down into [ANTERIOR, LATERAL, POSTERIOR] heads. For each exercise, include step-by-step instructions, recommended [SETS/REPS] for hypertrophy, and common mistakes to avoid. Tailor the recommendations for [BEGINNER/INTERMEDIATE/ADVANCED] fitness levels, and suggest modifications or alternatives for those with [SHOULDER INJURIES/EQUIPMENT LIMITATIONS]. Explain the biomechanics of each movement and how it engages the deltoids specifically.