Not having read all the replies so far, I am sure there will be overlaps, but some of mine are:
Use supermarket reward cards. But not just 1, get them all. So you don't feel guilty about "shopping the offers" in the best one each week, while getting the rewards as you do. (You can go around a few stores if you have the time, but often the savings in money on groceries are wiped out by losses on petrol and time, I find at least). Also, make friends with your butcher, and fruit and veg shop, and fishmonger. You can get cheaper cuts, bones for stock, often they will do value deals, may keep good things for regular customers (e.g. if they know you love lamb breast and they only get 2 in, may keep 1 for you), and I often get "use quickly as at the end of useful life" veg on good reductions in F&V shop - which can easily be used fast or frozen. I also have a list started every week by getting everyone in the house to write up what they have finished (or preferably, have noticed is almost gone - it's usually when gone though!). Asian supermarkets are also great for cheaper ingredients, especially spices, rice, and tins like coconut milk and tomato paste.
Plan ahead - write a rough weekly menu (take into account the diary and days you need fast meals, and days you can spend time on 1 days meals and prep ahead for others). Check the SM offers as you do this, and look in cupboards to see what you already have as well. Use this to write weekly shopping list. Also, when looking at offers, if you have spare cash, buy ahead on storecupboard staples when they are on offer IF YOU USE THEM ANYWAY. And try to buy things in season as they will be cheaper (and you can freeze lots of fresh things to enjoy later in the year).
Find out where you have a good shoe mender and someone who mends/alters clothes. Buy good quality classic items for you and look after them. They will be well worth that extra initial spend as they will cost you pennies per wear over their lifetime compared with many cheaper items. (And look in the sales as many of these can be reduced a LOT but classics won't date). Keep shoes polished to protect them, and mend small items as you go (buttons, small rips, hems down etc). (I have a sewing machine but I am not confident for many clothing repairs so get those done professionally - but will do hems, buttons etc myself and make lots of home furnishings etc for a lot less than buying them).
Make sure the house is well insulated and sealed to reduce energy bills. Have as energy efficient a heating system as possible, and use low energy using appliances where possible (if buying new fridge, for example, get an A or B rated one). Put a thermostat control into the house to turn on heat only when it gets below a certain threshold you set - this means you can keep it at a comfortable level but not use the heating unneccesarily on warmer days. And don't heat the house very warm and wander round in t-shirts: wear a couple of layers and heat to comfortable temps (about 17-20 C is plenty warm enough). Thermal vests are readily available and very thin and discreet now, so you can still be well dressed professionally if need be but warm enough for the season. And don't forget to change the heating settings as the seasons change (so it stays warm enough as autumn and winter arrive, but not too hot as spring warms into summer).
Use linings on curtains to keep heat in. Blackout linings tend to keep heat in better, and there are heavier thermal linings available (especially useful on north facing windows and single glazing). Open curtains in south facing rooms to capture heat during the day.
Try to use the car sensibly - plan routes to get lists of jobs done with fewer trips and less driving between stops (so do the library, supermarket, menders, F&V shop, and dropping in to see favourite aunt for cup of tea - in one trip and in an order that reduces overall distance). Save up non-urgent jobs for days when you can do other things in that area (menders near coal merchants and charity shop means you can drop off to charity shop, collect mending and buy coal all in 1 trip rather than 3 seperate ones).
Use vouchers for tickets, outings etc. Look for free or cheap outings in your area - lots of local authorities run events in parks etc, stately homes type places can have free or cheap events, and often have cheap admission but loads of free space to have pcinics rather than use the coffee shop etc. We often bring a picnic on an outing, and then go to the coffee shop for "afternoon tea" rather than lunch - a hot drink and bun instead of a full meal. I tend to make sure I have a mix of healthy and treat foods suited for picnics/school and work lunches etc in my cupboards - fun sized or snack sized choc bars, multipacks of crisps, multipacks of cans of fizzy drinks, snack packs of jellies or cookies, individually wrapped flapjacks; different sized sandwich bags and plastic tubs to bring snacks of sambos, raisins, fresh fruit, homebaking etc with us; and a couple of travel mugs and flasks to bring hot drinks on days that they are more needed.
I tend to buy multipacks of cans of fizzy drinks, as bottles go flat in our house - so we can have one when we want it but not waste the rest (or feel we HAVE to drink the rest). I use clippit type closures for big bags of crisps, nuts, popcorn etc (pour out a bowlful to share and then close the bag). I often buy bulk size packs of things and decant what we'd use into smaller containers that are easily accessible in the kitchen with the rest of the big pack on top of the cupboards out of sight.
I grow some veg in the back garden (pocket hankerchief size). Cherry tomatoes in a hanging basket, dwarf french beans on toilet windowsill (surprisingly prolific!!) and lettuce and sring onions in pots and among the flowers. 2 courgette plants between flowers gives enough courgettes all summer for us, and other individual plants that give a good return for space used are broad beans, brocolli and brussels sprouts (all amongst flowers), climbing beans and climbing beans (I grow those against the fences behind the flowerbeds and they just melt into the background and make the garden feel larger with the greenery!). And a couple of pots of herbs are great to add flavour and keep the costs down compared with supermarket packs.
While I tend to buy a lot of classic items for my clothes, for DD I am more of the "lots and cheap" variety. I don't buy the cheapest, but I don't tend to spend huge amounts on individual items for her (no uniform, so lots of tracksuits needed). As she's now not growing as fast so lasting longer in size in clothes, I am buying decent tracksuits and jeans for her (H&M, M&S, still some Primark). But I also have a supply of patches for jeans to iron onto holes in knees, and have made jeans with knees gone beyond use into shorts for summer wear.
We use the library a lot (free here, was a small fee annually where I grew up), for borrowing books, cd's, audio books, dvds etc. Handy to try out new recipe ideas or learn practical skills too as lots of different options.
I do buy a lot of books too but I use a reward card in the main store I use so get some reductions. (And other reward cards are very useful - Boots is good, my local chemist has a 10% reduction card they give to regular customers that is not advertised, my GP also has a similar scheme (we pay the Dr here), and there are cards which get stamped for lots of places we use - coffee shops, mini golf, indian takeaway - if you go there any way regularly, they do all add up and keep bills down). And the local card shop near my office does a "clear out" of old stock a couple of times per year - I always browse that well and re-stock my supplies, which means I am usually ok if last minute invites come up and it saves me money sometimes on other events I know are coming up. I also buy ahead, if I have money to do so, in the sales for birthdays, Christmas, and other occasions and to keep a stock of "emergency" presents for any occasion (present for a friend inviting us to dinner, "Thanks for minding the cat", "under the tree" presents for the neighbour who sometimes calls with a gift and for a glass of wine at Christmas etc). And I research a lot of my purchases online ahead of time - to get what best suits the need (whether a gift or household item) and also to compare prices.
This is probably long enough so I will stop there.