Systematically go through the moneysavingexpert budgeting stuff. Sign up to their weekly email for ongoing tips.
Use up all the food, toiletries etc that you have in stock. Buy as much food as possible from Aldi, Lidl or on offer in future. If you're careful there's loads of stuff that you will never need to pay full price from a main supermarket for.
Think about how much the meals you eat cost to make and ditch any of the expensive ones for cheaper ones.
Train the cats to hunt for their own food.
. Failing that, I've found that the Aldi foil tray food will actually be eaten by the fussy buggers.
Can you switch your overdraft to an interest free credit card, cancel the OD and make a point of paying it off during the interet free period.
Never eat at a chain restaurant or go to a theme park etc without looking for a voucher code. There's almost always a deal on offer.
Look out for annual passes for local attractions that you like to visit a lot. Sometimes they pay for themselves after 2 or 3 visits and after that it's a cheap day out.
Also see what is available locally. Our city has several large city parks with playgrounds, woods, lakes, wildlife that are totally free and a great way to spend an afternoon as long as it isn't raining.
Always take a picnic. Food and drinks out of the house can add up hugely. Use refillable drinks bottles filled with squash or water instead of buying drinks from convenience stores etc.
Buy cheap DVDs from the pound shop or Music Magpie instead of new ones from the supermarket or going to the cinema. You can make your own popcorn for pennies too.