As others have been indicating; cheapest way to go is to cook at home and bring in the left overs.
For me I make big time use of a rice cooker; and do some one or two pot type dishes.
One of my favorite recipes is what they call San Antonio Rice:
1 cup uncooked rice
12oz of salsa
1 tbsp vegetable oil
1 cup canned corn kernels (love the ones with peppers in them)
1/2 tsp ground cumin
1/2 tsp salt (I leave that out

)
1 1/4 cups water
(I usually double the recipe and add a 1 pound of some sort of meat - usually what ever sausage is on sale)
With a rice cooker you can also use broth (either stuff you made from lets say chicken, or the "canned" stuff) to add some flavor to the rice. Tossing in canned or frozen veggies and some sort of meat makes for a complete meal.
One tip that I learned from a friend is to try to take an evening or two - or maybe a "lazy" day at home and cook multiple meals at one time. When I am doing a rice cooker dish; I often cook up a pot of spaghetti sauce - which I freeze. And then cook up a pot of pasta that I will use over a couple of days. Another favorite of mine is cooking up some home fries fired up in the grease of what ever sausage I will use to have something more than potatoes with them.
Some money saving tips on groceries:
- Check out Aldi's (
http://www.aldi.com/ ) Some savings can be had over the big grocery stores at times.
- For those in the US, also checkout Angel Food Ministries (
http://www.angelfoodministries.com/ ). I have used them for the last couple of months for my meats mainly. For those of us on time short days in order to go to multiple grocery stores to get the best prices on meats - they are not bad overall IMO.
- For reciepes and other tips on how to save some $ check out Hillbilly Housewife (
http://www.hillbillyhousewife.com/ ). Some are extreme

- but some make sense as well.