To improve your grades in the NPTEL Fluid Mechanics course, focus on mastering the fundamental concepts of fluid properties, statics, and dynamics. Practice solving numerical problems and case studies, and review video lectures, notes, and assignments regularly. Develop problem-solving skills using mathematical and computational tools, such as Bernoulli's equation and fluid flow simulations. Pay attention to key concepts like boundary layers, turbulence, and drag, and apply them to real-world engineering scenarios. Participate in discussion forums, clarify doubts with instructors or peers, and attempt previous year's assignments and exams to assess your knowledge. By staying consistent and persistent, you'll see improvement in your understanding and grades in the NPTEL Fluid Mechanics course.