The only way to save money is to spend less than you earn. So either cut spending, or earn more. Sounds simple, right?
The first place to start is a very detailed budget. You can't really look at making any changes until you've got this first basic step done. I could even send you a copy of my own budget if you'd like, just to get you started.
As I've mentioned before, one of the main factors leading to my divorce was my ex's destructive spending habits. I tried to stay married as long as I could, which morphed into me enabling her. In other words, long before divorce, I adopted a very frugal lifestyle just to keep us out of bankruptcy. Even now, my normal monthly living expenses are about $750, but I have to put back enough to be ready for big annual expenses like home insurance, taxes, etc., so really it's more like $1000. That includes tuition for D7's school & daycare a couple days a week; if I was really struggling she'd be going to public school and I'd rely on family members more for child care, and the Christmas budget would be really scaled back.
I outlined some ideas on saving money here:http://www.dadsdivorce.com/father_divorce_forum/viewtopic.php?f=8&t=38502&start=10