1)
After your opponent moves find all the checks, captures, and 1 move threats (like attacking an undefended piece).
2)
Then you can do whatever you normally do and find a move you want to play, but it helps to look for all of the checks, captures, and threats you can play. That way if there is a way to immediately win you'll find it.
3)
But after you've decided on a move, before you play it, imagine it as if it's been made, and from that new imaginary position, again find all of your opponent's checks captures and threats. This is to make sure your intended move doesn't immediately lose.
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All together this is what I call good calculation habits. Many years ago it's what Dan Heisman called eliminating "hope chess," and some popular youtube people bring it up from time to time too.
Anyway, even beginners do those steps sometimes... but your goal is to do them for 100% of your moves and in 100% of your games, and that's very hard. It takes a lot of practice to build up that habit.
It's also important to understand that you should do your best to not lose any material. Not even a single pawn (-1 point). Not even rook for a knight (-2 points). Sometimes people get stuck at lower ratings because they don't think pawns or knights are important... the reason even a single pawn is important is because if you continue to make equal trades all the way down to a king and pawn endgame, you'll eventually get something like this
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And this position is so winning that after 5 minutes of practice you could beat the world champion 100% of the time.
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Play time controls that are long enough that you can develop these good habits, and do your best to not lose any material... as long as you've learned other basics like opening development and forks, that's basically all you need.
Im not looking to become a GM or anything, I just want to be decent enough that I can play in a tournament and not get destroyed every single game.