What to eat beforehand?

I have a Turbo Kick Class tonight at 7pm. I will be my 3rd. I still havnt quite figured out how to plan how I eat around that time frame. The first day, I only had a snack about an hour before hand (I think it was a natures path granola bar), and then ate a Visalus shake when I got home. I went to bed feeling satisfied but not full. The second class (last week) I ate a small dinner 2 hours before, and I couldnt put my all into the workout because I felt heavy and sick. When I got home I couldnt even eat anything. I woke up the next morning starving!

How and what should I eat? I burn about 530-620 calories in a class (1 hour) if that helps.