We went through our bank statements and highlighted all the smaller, monthly, subscription stuff, and were shocked at how much all the smaller items add up to, so we've stopped most of them.
We keep tabs on phone, Sky, broadband contracts anyway, and have diary notes when the contract expires, so already change/downgrade or whatever immediately the contract ends, so we don't end up paying more than we need.
Having said that, even on Sim only contracts for the mobiles, I did a bit of shopping around and have changed providers to now pay half of what we were paying, now all 3 contracts are under a tenner a month, one is only £6 per month, so that's been good.
We don't do "top up" shops or end up paying over the odds from convenience stores for things we run out of. We already do a "carousel" of going to different supermarkets so we buy at whichever shop has the offers on that week, never pay "full price" for things like Heinz, Kelloggs, Loo Rolls, Washing powder, crisps, etc., as they're always on offer at one of the supermarkets in rotation. Online shopping apps tell me which supermarket has the deals on that week, so that dictates which shop I go to that week. I stock up when things are on offer, so I am a bit of a hoarder, but it saves a massive amount of money.
Meal planning is also a big money saver as there's virtually no waste from buying too much of something or ending up throwing away things that have gone out of date.
Likewise spent quite a bit of time shopping around for car and house insurance - the savings can be quite enormous so well worth the time.