Sherpa is the way to go
Sherpa is honestly the best way to go when it comes to GMAT prep. There is too much content to consume if you try to study on your own and I can promise other instructors do not compare. Nafeez is passionate about teaching his students GMAT tricks. He has methods for breaking down solutions to every question type. The benefit to taking his class is that he takes overwhelming subject matter and chops it up into small, manageable bites. Also, his class goes beyond the GMAT and starts to train you how to think like a business student. AND if life gets in the way of your studying, Sherpa offers 1 free re-take of the class. I would highly recommend this to anyone taking the GMAT.