One of the ways that I cut costs on food is by determining the absolute best price for items we buy often, such as tomato sauce, and then I figure out how I can stockpile that item at the best price. A while back, I started buying the big cans of tomato sauce (that cost less than $3 and are organic) at Costco instead of the individual cans. I then take the tomato sauce from the big can, repackage it into freezer bags (2 cups per bag) and then freeze it so that I have individual portions (I get six 2 cup portions) that I can grab when I need it. I usually do not take the time out to thaw the sauce before I need it unless I actually think to do so, but I have found that once I stick it in a pot with the other ingredients, it thaws fairly quickly. If I am using it to make pizza sauce and have forgotten to thaw it, I will do so either in a small pot on the stove or in the microwave. You can also thaw it by placing the bag in cold water for a while.
I also buy most of our produce such as bell peppers and onions at Costco and when I chop up some for a meal, I chop up extra to put in the fridge or freezer for other meals. If I have extra time, I will chop up a big batch in the food processor for the freezer. When there are sales on these items, or if I find them on the discount rack, I will buy extra for the freezer.

For meat, I always buy a bunch of whatever has a really good price and then I repackage it if needed and stick it straight in the freezer (unless I am going to use it for dinner that night or the next night). I do not buy meat every week because I save my money up for the good sales instead. I always have enough meat available in the freezer so if there isn't anything good on sale, I will just use what I already have on hand. I also make sure that I use the older items from my freezer before the new stuff I put in. Throwing out food because I left it in the freezer too long is a very sad thing in my house and I try not to let it happen as much as absolutely possible (yes, I do slip up sometimes and things are forgotten about until it is too late). To save time, I try to cook up extra meat and put half in the meal and half in the freezer (or in a second meal, etc.). For instance, tonight I am trying out this
Beef Cabbage Soup recipe (I am using navy beans instead of kidney because that's what I have and I didn't add the sugar. I am planning on tasting it at the end to see if this is necessary or not. May spice this up a bit with some cayenne pepper) and I cooked up the ground meat (I used a 1.25 lb. pkg of turkey instead of a lb. of beef) with the onion and bell pepper. Then I put half (3/4 lb. each) in the recipe and half in a bag for the freezer. This will be great for all sorts of things, from tacos to shepards pie, to soups.