Regular saving, and cutting back it's as simple as that, and looking at how you're spending your money or getting into debt if it's applicable.
I used to be in a bit of debt a while ago, but got myself out of it.
For mortgage and bills, at paydays; everything that needs to cover those, goes into the account they all come out of, everything else is in my current account, and is either moved into an ISA or into my starling savings account, after some is held back to spend over the month.
I use a Starling account as it works for me, I think other accounts can work similarly, it allows you to start different savings pots for various different things. I have savings pots for everyday regular/yearly occurrences, like running a car, running a motorbike, birthdays, Christmas, then other long term more expensive things I'm saving up for like a couple of holidays I plan to take many years down the line, a new motorbike etc. I'm only saving smallish amounts into each pots each month, but it adds up.
When things like my car insurance and bike insurance would come up for renewal in the past I used to just pay it on a credit card and suffer the interest and pay it back, but now with saving like I currently am, I break down the expected cost over the year and save that monthly over the year, then withdraw from the pots when I need to pay my car insurance or buy VED for the bike etc.
And it's lambasted about whenever someone mentions cutting out lattes and avacado on toast, usually when its a boomer telling you, but I'm only late thirties and yes, it does help, cutting out frivolities and things you actually can live without, helped me and my partner towards saving for a house deposit, and is helping saving now, a recent example for me personally would be I went to the local shopping mall place, and where I'd normally every other time, stop and get a coffee or a bottle of something to drink, I took a coffee from home in my insulated cup, and bottle of water and stuck it in my bag, zero spent.
But it is not a case of cutting out everything totally for me though and living like a monk, but finding the balance between what you actually need, want or what will actually give you joy is the balance, a £6 coffee; drank in 10 minutes and forgotten about later that day starts to look like less and less worth it, as other things you actually need to spend money on spiral endlessly out of control price wise, like car fuel and basic groceries.
I spent the best part of my 20's and early 30's getting into debt, buying shite I didn't need, but made me feel good buying it, I've had a change of view on how I view possessions and over consumption now, selling a lot of those things I bought over the years to recoup money to put into savings.