Have you familiarized yourself with Amy Dacyczyn of Tightwad Gazette fame? Get her book, and follow her thought patterns. They will not steer you wrong!
Mostly, she thinks along the lines of pricing out some meals that you like, and eating the ones that are on the cheap end, more often than the ones that are on the more expensive end.
Also, base your meals around ingredients that are the most affordable, and cook from scratch rather than buy packaged crap. Also, make substitutions all over the place, to favor inexpensive ingredients. Why eat jasmine rice, when un-fancy rice will do just fine? Why use pricier starches when you can get a sack of potatoes for pennies?
Most people aren't willing to do the work of figuring out the recipes and the portions and the methods that can help them eat for pennies and enjoy their food tremendously. But if you ARE willing to do the work, you will reap the rewards!
Personally, I LOVE beans and lentils and think these taste delicious cooked from scratch. I cook with normal yellow onions, and simple, cheap spices, like oregano, or like chili powder. I think that if I wanted to save money on food, I would eat more of the inexpensive meals, and drink more water between meals.
Above all, do you know the phrase:
What gets' measured, gets done.
Basically, if you want to get your grocery expenses way down, keep track of how much you are spending per meal. How much did you spend on 1/3 of a bag of lentils and one onion? And price out the sides -- your carrots, your apples, your whatever. Once you've got a sense of accomplishment about having two or three super-duper inexpensive and satisfying meals, move on to develop two or three more, and cycle them in. Easy, right?
To figure out how to put meals together, read Dr McDougall's recommendations and Jeff Novick's guidelines.
There are no shortcuts, but hopefully you think your health is worth it!
