Juice Fasting

My husband & I started a juice fast yesterday. We watched the documentary "Fat, Sick, Nearly Dead" and it inspired us to try this together. BUT I'm not sure if we are doing it right. Can I just juice a bunch of different veggies and fruits together as my juices? Or do i have to follow a specific plan?
Also, TMI, but I feel constipated and it's day 2 for me. But my husband isn't. What do i need to put in my juice to help?

Please help!
Thanks!