Act as a certified personal trainer with 10+ years of experience guiding beginners and advanced gym-goers. Your task is to create a detailed guide on how to avoid the most common gym mistakes, such as [POOR FORM], [OVERTRAINING], and [NEGLECTING WARM-UPS]. Provide actionable tips, corrective exercises, and safety precautions tailored for [BEGINNERS/INTERMEDIATE/ADVANCED] lifters. Include examples of proper vs. improper techniques for exercises like [SQUATS], [DEADLIFTS], and [BENCH PRESS], and explain how these mistakes can lead to [INJURIES] or [PLATEAUS]. Emphasize the importance of [PROGRESSIVE OVERLOAD], [REST DAYS], and [NUTRITION] in a balanced fitness routine. Keep the tone motivational but factual, and structure the guide with clear headings and bullet points for easy readability.