There are a lot of things you can do. You can find a lot of excellent tips in the books by Amy Dacyczyn. She wrote The Tightwad Gazette. These really helped me out a lot with my first son. I wanted to be a stay at home mom with him and with the help of the ideas in these books, I did it.
Here are some of the ideas.
Start shopping yard sales... you'll be surprised at the clothes you can find there... especially kids clothes. And if you live in or near subdivisions. Thrift shops are also recommended, although I personally do not like them. It seems like the ones I've been to don't have very nice items.
Keep a price book of your local grocery stores. You can make this up yourself. Start writing down the prices of the items you normally buy and then find out what they charge for those items at each of your local stores. Then you'll know where to get the best price and when they have a sale, you'll know if it's a really good sale or not. If it's a great price, buy lots and stock up. A deep freeze is a good investment for this.
Stop eating convenience foods and eating out. Cook at home from scratch and only eat out on special occasions.
Look at your monthly bills... and figure out where you can cut. Examples to look at would be cell phones, expensive calling plans, expensive cable or satellite bills.
Don't buy items at quickie marts... they are expensive!
Never buy a brand new vehicle... shop around and buy a good used vehicle.
Lower your electric bill, by turning off lights when not in use. Wash dishes by hand and line dry your clothes if possible. Dishwashers and dryers are big energy drains.
I hope you can use some of these tips and find those books by Amy Dacyczyn.
You can live on a lot less with a little elbow grease and some creativity. Good luck!