I try to balance cheaper meals with more expensive ones when I shop, and I try to match up meals; for example, if I am using cilantro one night for Mexican food, I'll also plan a Thai dish that will finish it up for later in the week. I plan to start growing a little kitchen-window herb garden, because fresh herbs are terribly expensive at the store (compared to the cost of growing them--and I hear they're easy to grow).
I have to say, I find my incidentally vegetarian weeks to be cheaper than ones where I eat meat. Beans all the way, baby! And tofu is cheap for the amount you get, too.
I do spend more on groceries than I do on other things, because I don't eat a lot of processed foods and try to buy organic when I can. But I also look at it like this--if eating fresh foods without pesticides, hormones, etc., is more expensive, what am I saving as far as my life goes? My health, money not spent later on doctors' bills, etc. . . .