Act as a certified personal trainer with 10+ years of experience specializing in muscle definition and strength training. Provide a detailed, step-by-step guide on the [TOP 5 EXERCISES] for achieving well-defined arms, targeting both the [BICEPS] and [TRICEPS]. For each exercise, include the proper form, recommended sets and reps, common mistakes to avoid, and modifications for [BEGINNERS] or those with limited equipment. Explain how these exercises contribute to muscle hypertrophy and overall arm aesthetics. Tailor the advice for someone with a [MODERATE FITNESS LEVEL] looking to enhance definition without excessive bulk.