Meal plan - its fun once you get into it. My teenage son loves it, and has even started cooking with me because he's interested in the meals hes chosen.
Pay in cash, not by card. Only take out a set amount each week, and stick to that amount. You quickly relearn how to add up as you shop! And if you don't have the cash, you cant buy it.
Look out for freebies, discounts, offers. There are lots around.
Join money saving expert, read the valuable advice, and read/join the very helpful credit crunch forums.
Walking is free, and family friendly; cycling good too, if you have bikes.
Walk whenever you can. Healthier and if you have a vehicle, cheaper.
Make do and mend, the old wartime slogan! Thrift is back!
Batch cook, and freeze.
Take small picnics, snacks, and flasks of hot chocolate when you take kids out. Mine loved picnics when they were little, whatever the weather! Buying food and drinks out really mounts up.
I am gradually whittling away a big whole heap of debt this way, and now that I'm becoming much thriftier, I can't believe how much money I wasted in the past!