If you're currently a snacker, I'm of the (likely unpopular opinion) that just trying to stop entirely and suddenly probably won't work, especially in the longer term.
I used to be a massive boredom snacker, and a kind of replacement therapy was an absolute godsend for me.
I'd start by replacing your usual snacks with lower-calorie options – instead of crisps, biscuits, etc, look for things that are flavourful and crunchy and low-calorie but somehow satisfying.
I find very salty / vinegary things get rid of my snack urges quickly, so I keep a jar of little pickles in the fridge for moments when I want to reach for crisps.
Sliced cucumber and tomato with a little bit of salt or feta or balsamic – a bowl of it in the evenings, eaten slowly (while I'd usually be mindlessly jamming chocolate in my mouth) is oddly satisfying, and mostly water.
Baby carrots, popcorn, melon, peas and pesto... Look out for nuts, as they're super-high-calorie despite being 'healthy'.
It all looks a bit odd written out like this but I've found switching to these kinds of snacks has made a MASSIVE difference to me – it gives my mouth something to do without creating the sugar / carb spike that used to leave me wanting another snack not too long after the first.
Plus, protein and fibre, protein and fibre, protein and fibre. The more of those you can get into your meals, the more satiated you'll feel for longer throughout the day.