To achieve major gains in fitness, start with a structured strength training program that targets all major muscle groups at least twice a week. Prioritize compound movements like squats, deadlifts, and bench presses to maximize muscle activation. Ensure progressive overload by gradually increasing weights or reps. Nutrition plays a crucial role; focus on a high-protein diet that supports muscle repair and growth, complemented by healthy fats and carbohydrates for energy. Stay consistent, track your progress, and allow for adequate recovery through rest days and sleep. Lastly, stay motivated by setting clear, achievable goals and celebrating small victories along the way.