Take advantage of balance transfer and interest free periods on credit cards. Get a credit card, transfer any small debts onto it, with no interest for say 9 months (make sure they don't charge any percentage for the actual transfer though, we found that Egg didn't, hope that's still the case) and then set up a direct debit to pay the same amount each month for those 9 months. When the card arrives, destroy it though!! 9 months or however long later, do the whole thing again - transfer your now very much reduced balance onto another card with no interest. You'll know exactly what you owe, and it won't increase at all. Little bits of monthly interest on a few small debts will quickly add up to a figure you'd rather not be paying!! Credit card companies fall over themselves trying to offer good deals, in the hope that at the end of the interest-free period people won't bother to switch again. Play the system!!!
Also, use saucepan lids when cooking - speeds up the process so you use less energy. Put the plug in the basin when you wash your hands. Use the "time saver" function on your washing machine if you have one. It shaves a few minutes off each bit of the cycle.
But the best one, by far, is to write to food companies if you love/hate something. Either way, they're very likely to send you loads of vouchers. Someone told me this ages ago, and it's TRUE - I've done it!