6 years ago we decided that we had to pay back all our debt so over the years we have developed a very frugal lifestyle. We didn't start all of these things at once - it would have been too much...
We do a monthly shop paid for by debit card & I pick up milk (cash) from the Waitrose at the station when I am rushing to get my train home (annual season ticket - saves 60% on daily prices).
Freesat TV.... no Sky subscription. Films from the library or the bargin bin at the supermarket - if the film was good, it will still be good a few months later. Books from the library.
We only have one car and walk / cycle wherever possible.
The monthly shop (from Aldi & international supermarkets mainly) includes stocking a sweets and treats cupboard and the kids (and dh) know when that is empty it doesn't get refilled until the next monthly shop. The first few months they ate everything inside a couple of days... now they make it last.
I do a rough meal plan for the month and keep a well stocked store & spice cupboard. The plan has the basic all the time meals and something different for the weekend planned into it. It helps if you can think on your feet and have an encyclopedic knowledge of recipes so if something is out of stock or on special you can do a mental substitute. I would highly reccomend The Flavour Thesaurus by Niki Segnit for inspiration for putting new flavours together - very helpful for the end of the months when the meal plan has gone a bit wayward.
We also try to cook seasonally & from scratch because it works out cheaper. I learnt how to make those things that make life nice, but are expensive to buy (most are really easy but difficult to transport / come in a nice packet / have big marketing budget) - totillas, chapatis, sourdough bread, beer, wine, flavoured vinegars & oils, "nice" biscuits, dips, crackers, cheese straws, energy bars, hand cut vegetable crisps.... If something is really cheap it is used to make pickles, sauces, jams ect. So this month is marmalade, chocolate dipped orange peel and sourkraut month. March will be used to salt lemons because there will be loads left in the supermarket after pancake day (usually!) and mango chutney. During the Summer months I make the years worth of strawberry & raspberry jam and tomato sauce. Autumn sees the plums and apples making brown sauce & chutneys. Next years mincemeat was made with the special offer dried fruit. It is all about taking advantage of what is there - we had a bumper crop of blackberries in the hedrows this year so we have blackberry jelly in sauces instead of red current jelly from the supermarket. Put them in nice containers in the cupboard and nobody knows you are as poor as a church mouse.... I get my posh jars & bottles from the recycling bins
& make my own "craft" beer bottle labels on the printer for when we take them to parties.
All the bills are paid for by DD on the day after payday so we don't rack up bank charges (previously been an achillies heel). We don't have credit cards, but have a regular DD to a sinking fund account to pay for when the boiler breaks or the car needs to be fixed. For any big ticket items we save up for it.
Phones are on capped contracts - 12 / month.
We have stopped buying clothes unless it can't be avoided - school shoes, new uniforms. A friend of mine is a hairdresser so I alter her charity shop bargins in return for haircuts. When clothes are ready for the bin they are deconstructed for the zips, buttons and useable fabric. Even plastic carrier bags can be made into plarn or plabric (iron layers together to make a waterproof fabric) for making shoppers.
Skip diving - it is polite to ask, but as it costs per ton to landfill waste most people don't mind. If you have a woodburner - offcuts from timber yards / joiners burn just as well as logs bought in. Some building sites have half used tins of pain etc that will just get binned, but are enough to redo a hall / bathroom.
Kids gifts are usually craft kits made up from cheap sources... print making templates & paints, sewing projects, book making, crochet, knitting, models ... instructions can be found on line & reformatted to make them look as if they are bought - including a barcode if you have people on your gift list that turn their noses up at "handmade". There are also good sources for party bag fodder on line. Adults get a hamper or an Art Photo (husband is a photographer) Gift tags are made from the box of shop tags bought for a fiver from a shop fitter supply store - just have a picture stuck on, or my talented DD does a cartoon of the recipient on them. Wrapping paper is hand printed from a plain roll (same place as the tags).
And as has been said up thread - don't buy impulse / non essential things on the day you see them. Stop & think if you really really need them....