Read a chess book. Here are a few good books:
"The Mammoth book of Chess"
"Logical Chess move by move" by Irving Chernev. It teaches you how to attack the king in the king pawn openings and how to play positional chess with the queen pawn openings.
"My System" by Aaron Nimzovitch.
"Think Like a Grandmaster" by Alexander Kotov. This book explains how to analyze variations so that you can play the middle game at a much higher level.
"Judgement and Planning in Chess" by Max Euwe. A classic book that explains how to judge a position based on space advantage, combinations, endgame advantages, king attack, and pawn structures.
"Bobby Fischer Teaches Chess" by Bobby Fischer. A classic book that teaches chess tactics for the beginner.
"Chess Master vs. Chess Amateur" by Max Euwe and Walter Meiden. This book explains how a master beats an amateur by making the right move based on a position's needs.
"Practical Chess Endings" by Irving Chernev. 300 endgames that start simple but end difficult.
"1001 Checkmates" by Fred Reinfeld. A classic book that will help you to see checkmates and calculate the variations.
"Ideas behind the Chess Openings" by Reuben Fine. This book explains the strategies behind the openings so that you can remember and play them better.
"100 selected games" by Botvinnik.
"Basic Chess Endings" by Reuben Fine. This is a thick book that is a classic and explains all types of endings.
"Point Count Chess" by I. A. Horowitz. It's a classic book that rates 32 positional features and teaches how to convert these 32 advantages into a win.
"How to win in the chess endings" by I.A. Horowitz. This book explains endgame strategies without complex variations.
"Chess Fundamentals" by Jose Raul Capablanca. This book teaches the opening, middlegame, and endgame strategies.
