I have a budget of £50 a week between me and hubby and we don't scrimp on anything, and we're never hungry! But it does reduce the amount we waste!
I plan what we're having for dinner/lunch for the week. Once a month i'll buy a big pack of turkey mince and split it in two, make a big pot of chilli and a big pot of bolognese, then freeze it in meal sized tubs for during the month. It's also handy if you don't have time to cook something from scratch!
Once i've planned the meals for the week, I write down all the ingredients i'll need to buy to make them. I try to have things that use similar ingredients. I use a lot of peppers and chicken in recipes so I'll buy a big pack of chicken and split it down into pairs of breasts in food bags, then shove them in the freezer (to stop them going off before I use them).
I also try to get the furthest away dates (obv.) and use the meat in order of date that it goes off.
I use a lot of frozen veg which quite often works out a lot cheaper than fresh/tinned and tastes just as good! I always have a bag of chopped onions, peppers and peas in my freezer! I use them in EVERYTHING.
If you have an Aldi near by, go there and get your fruit and veg. It's always good quality and they do their super 6 every week where they have 6 fruit or veg priced at 69p. Excellent value. Well worth the detour!
And as others have said, own brands as far as possible. I too only buy coca cola brand diet coke, but try other things, some of them are just as good as the big brands!