Do you make a menu for your shopping list? I found that if I planned all my meals out in advance I was less likely to spend more money later in the week getting things to make for a meal that wasn't planned.
I have gotten to where I do this all the time now. I have learned that by planning out the meals and menus so that they use similar ingredients, I can buy fewer items in larger quantities. I am actually saving a lot of money on my groceries by doing it this way. I have also gone back to old school ways of cooking. I make a lot more things from scratch and avoid spending extra money for prepackaged foods that I can easily make myself. I think it is healthier, too!
I have a number of dishes that I'm fairly good at and I mix and match them to make meals for a week. When I have the menu for the week I go and pick up all the ingredients and that's basically it for the week. It really saves on alot and since we have a Little Cesar's pizza here and there to break things up a bit I end up saving alot from not buying out of hunger or boredom or whatever.
Yeah, it also helps when you can use leftovers from one meal into another meal the next day. One thing I like to do occasionally is make a pot of refried beans in the crockpot - then using the unmashed beans to make a soup one day then using the rest for burritoes. You can also use them for nachoes or just freeze them for quick and easy meals for my hubby for lunch. (He really likes rolled up tortillas with beans and cheese for lunch.)
I find that in general all the things I cook require the same ingredients, and so I have a pretty good idea of what I'm going to buy from the grocery store, even if I don't know specifically what I'm going to cook that week. That's probably pretty good evidence that my life is boring, though.
I don't plan my meals in advance. I don't cook that much, as my partner and I like to try new places to eat (and there are plenty of them in our area). However, if we feel like eating a particular home-cook meal, then we'll go out and buy the ingredients then.