A Good Instructor
A good instructor doesn't train your dog. A good instructor teaches YOU how to train your dog.
Your dog will only improve if you do the work and practice in the environments your dog will live in and experience. No dog will improve if you only practice in class.
How to Succeed
Ask your trainer questions if you have any or don't understand something. Listen to your trainer fully as seen "snippets" of information are important. Participate in class so that your trainer can see that you have a good understanding of how to help you with your dog's learning.
Go and practice the skills you have learned, every day, out in the real world: your home, yard, car, on walks, etc. You learn and practice in class, but you also need to make sure your dog learns and practices outside of the classroom.