I spent a few years of my life backpacking in a few countries and learned how how to manage my stuff in order to live out of a 35 litre backpack. I had to be mindful of what I took with me with such limited space.

I've since carried that approach to my life at home and tend to be proactive in dealing with what I buy and own. One way I try to be proactive is to make a list of stuff I want or think I need instead of buying it as soon as possible. Most times something sits on the list for a long time and I'll just remove it. It's a good indicator that I don't need to buy it and it will only cause more clutter. This is sort of something I made up over time to work around my adhd impulsiveness so it may or may not help others.

Make sure there is a set place for each thing, and make sure you always put them back there. Taking just a second or two to put something away properly will prevent you having to do hours of organising and tidying later. It'll also make it easier to find things, so you'll save time there too.

Everything has its place. Before I buy something, I figure out where it needs to go. Preferably I get rid of stuff before I get something new, so I don't accumulate too much.

Storing things as close as possible to where they are used, and in a way that is very easy to put away even if that makes it more difficult to get out.

Strategic duplicates when something is used in multiple places (e.g. pens and pencils both in the home office for work use and the livingroom for tabletop RPGs).

Only having one option when I don't need the strategic duplicates, so there's no decision-making required (e.g. one handbag, one belt, one backpack).

Always be pruning away any objects you don't immediately need that day, putting them away.

Always leave at least one square foot of empty space on any countertop, desktop, table, etc, so that you have somewhere to put things down upon returning from a trip out of the house.

Like others have said, try to have a place for everything, but I have a couple of caveats. I have a spouse and two young children, so having a specific spot where everything always goes is not really feasible. I try to restrict things to specific areas, like specific drawers/boxes/containers for it's if a certain kind. This keeps clutter out of sight, and having a policy that every item lives within some kind of container allows me to control how much space I want to allocate to a category of items. For example, my kids love figurines and action figures; they have a box for those type of toys, and once the box gets full, they have to let go of some if they want to get something new.

We also have areas in our house where things are allowed to be "parked," but the parking lot has to be cleared everyday, so that every day begins without clutter/chair. These are mostly our flat surfaces, like the eating table, kitchen counters, coffee table, etc. Part of our nightly routine is to run around for 10 minutes cleaning off these spaces.

One way is to get a big dog, I used to have lots of clutter, but having a dog that can break or eat nearly everything in reach makes my move things to less accessible locations or by necessity removed from my living space.