How do you balance between a full time job and studying?

I currently work full time and I will start my Princeton Review's GMAT prep course next Monday(6/24/2013). I am equally excited and nervous about this because I know once the class starts I need to be studying every single day. I just wanted to ask everybody out there who has a full time job and are studying for the GMAT what your suggestions and advises are on balancing your life. How many hours do you study a day, a week?

Thank you so much in advance for your tips!