I went cold turkey on my absolute nemesis foods 2 years ago this month. Haven't eaten one since.
I went nearly cold turkey on all crisps, bought biscuits and cheap chocolate as well. Not entirely, I still slip up and e.g. I'll eat them if I am out, but day to day I don't buy them and I don't eat them.
If it has to be a specific thing, I think that's the one thing I would isolate, but also it's been a case of marginal gains:
E.g.
I vaguely try and eat within an 8 hour window, but I do that by pushing breakfast back but if I am really hungry one day I just eat breakfast. Similarly, if I am working from home I will have tea at maybe 5-6pm, but if I am out I don't worry about what time I am eating. So it's still flexible enough to fit round my life.
I sometimes have a protein shake (banana, protein powder and fat free natural yoghurt) for breakfast, because it's filling and ups my protein intake. But if I don't fancy it I eat something else. But I don't Mainly eat e.g. a bagel or crumpets for breakfast any more.
I try and have chicken breast with more meals, again to try and consume more protein.
I try and pick a few more tomato based pasta sauces over and above ones made with crème fraîche. I don't usually have garlic bread any more.
I mainly try and minimise calories through drinks - so not buying fruit juice, sometimes drinking less wine. I have unhealthy cereal in the house but it's to stave off omg I need a treat corner shop trips - that works for me but wouldn't work for my brother.
I don't treat every time someone offers me a treat as an opportunity to say yes. Sometimes I remind myself that I would rather say no now than have to say no later.
None of these things are all or nothing - sometimes I really fancy some fruit juice or a creamy pasta sauce. Anything that's an all or nothing thing doesn't work for me. And everyone's areas where they accidentally get extra calories they don't need will be different. I wasn't a big drinker - that might have been more of a focus for change if it was.
So I guess my broader one thing is don't dismiss marginal gains or a "when you can" approach. It's Way Way better to overeat and then go "oh, I've over eaten" and carry on as you were, than to overeat, panic, give up and try again in 3 months time when you're half a stone heavier.