Written by Saul Magnusson
This is a guide for improving at chess for persons of ANY level. There is a lot to know about chess, and, in fact, more books are published about the game of chess than about any other game. But, of course, improvement doesn't depend on your equipment or library but the quality, regularity and effectiveness of your practice. And good practice can be very straight-forward.
The general training pattern is this, and you're free to modify it to suit you.
Study my recommendations over a four week period, for an amount of time each day based on your level of commitment. Then, after a short break, repeat the material, this time in a period of two weeks or less. The material to study I give below. If you're a complete beginner, start at level 1. Otherwise, start at a level you already know. (i.e. if you know how to move the pieces but aren't sure about checkmating with a queen start first again at how to move the pieces)
Level 1: How the pieces move and special moves like castling and en passant
Complete the series of exercises called "Chess Pieces" here: https://lichess.org/learn then complete "Fundamentals", "Intermediate" and "Advanced". You may wish to make an account to save your progress but its not required and the site is easily navigable.
Level 2: Checkmates on an empty board and tactics like pins, forks and discovered attacks.
Complete only the "Checkmates" and "Basic Tactics" on this page https://lichess.org/practice then proceed to the next level
Level 3: A first set of tactics
Create a lichess.org account and go to https://lichess.org/training to solve puzzles. Set the difficulty level to Easy or Easiest. Spend at least 2 minutes trying to solve each problem, but perhaps not more than 5 before making your best guess. The puzzles you receive will adapt to your strength so don't worry if the first few are incomprehensible.
After the four week period, review all the practice modules and every puzzle you solved in that period. Your puzzle history can be found in https://lichess.org/training/history and you'll have to right click and open each puzzle in a new tab. This is an important step. Reviewing puzzles you have already solved will reinforce your knowledge of important patterns more effectively than solving a new puzzle and will also confront you with patterns that you may have missed the first time. If you solved 10 puzzles a day, you will have to aim for double that amount to solve the set in half the time.
You may want to play some games of chess online or against your friends. I suggest you try to limit these to at most three per week and to review those that you do play to identify and correct any mistakes. Intentional and focused practice is far more valuable than playing. This is advice I follow myself.
While there are other areas to chess such as the memorization of openings or exhibiting correct technique in endgames, tactical ideas persist throughout the entire game including those two phases. 42% of games between grandmasters and 75% of games between strong club players are decided by tactics. So persist in your study of this element of the game.
Please feel free to reach out to me at firstname.lastname@example.org to let me know about your plan to start or the improvement you've experienced using this method, it will help me understand and improve these recommendations.