Play chess.

>>34769287
What do you mean by "good"?

>>34769287
Play chess. A little longer games, so you actually have more time to think. Solve puzzles on lichess.org. Solving puzzles is very important, trust me. Repeating all the different patterns is very important. Especially if you want to play quicker games and avoid making beginner mistakes. I probably spent around 70 % of the time im my chess club on solving puzzles. The rest was theory. I think for theory I did read Aron Nimzowitsch "My System". It gives you an solid allrounder on theory. It has been a while though, so I don't remember. If you are beyond the beginner phase, drill different openings in your head. And also try to understand the logic behind the moves. Try getting away from the basic stuff like the italian opening for white. A few years back most people I played against didn't know how to play queens gambit with black. So they blundered most of the time. Choose unusual openings in the beginning. For black I used Caro–Kann Defence, because you can play it against most openings. There were a few good youtube channels that discussed different games. They were solid though.
I don't play anymore though, so my memory is a little shit.