If you're not lucky enough to have a Lidle or Aldi nearby, you can still save at the supermarket by shopping down a grade.
If you always buy the top brands, give the store own brands or economy brands a try, you might find there is little difference in taste but you do make savings.
If you splash out on a takeaway each week, try buying a similar menu from the supermarket ready meals, you mght enjoy it even more as you are making a saving.
If you live alone, frozen vegetables can be useful, with no waste. Try frozen mash as a good stand by.
As pp have mentioned, don't waste food. Frittata, toasted sandwiches and pasta bakes are good ways to use up leftovers, also butter beans, chick peas, haricot beans can help sretch soups and casserols.