Also cut down on the number of nights per week you eat meat- we only have meat meals two or three nights per week and it does save loads of money.
Second all those who say meal plan, too.
Buy Christmas decorations, wrapping paper, presents etc. in the January sales- we never buy crackers and suchlike full price.
I buy generic presents and cards whenever I see them on sale, and I no longer have to rush out and spend £10 on a present for a child's party. Given that there is a party every other weekend when they are little it really saves a lot of money. I saw Barbie dolls for 99p in Sainsbury's the other day and bought three of them as I know they will come in handy for birthday parties.
I have a big present box which I keep all these things in under our bed.
And for petrol- don't fill your tank up fully unless going on a long journey- I never put more than £20 worth in at a time and although I have to fill up more often it serves to save money in two ways- firstly I am more economical with journeys if I know I have not got a full tank, and also if you have a full tank the weight of the fuel actually decreases fuel economy.
We have a nice fleece blanket tucked down by the sofa- if you get cold while watching TV it's easier to pop that on instead of turning heating on.
Also, I believe it is cheaper to have the heating on all the time on a low level than to keep reheating it from cold, say twice a day. But that might only work if you have a combi boiler.