Aman Hambleton has an EXCELLENT although very long series on Youtube called Building Habits. He starts at a very low ELO and follows a set of basic rules. He loses several games but his win ratio is high. Once he gets to a higher Elo he has to introduce new rules, and again it doesn't mean you'll win every game but you build good habits by practicing over and over again.

And so it continues. Here's the full playlist: https://www.youtube.com/watch?v=p8pZbhjL-fQ&list=PL8N8j2e7Rp...

If you are a beginner, studying tactics and doing puzzles. Always keep your pieces defended, even if there aren't immediate threats: undefended pieces may become tactical themes (which means, your opponent might be able to explore this two or three moves ahead). Always consider checks first, then captures, systematically.

A level up, studying openings.

Always go into a position with a plan (which generally means, which squares you want your pieces to occupy). A bad plan is better than no plan at all.

The plan must be continually checked with calculation (and here is where tactics is useful), and you must be ready to change plans if things don't go well.

You need also to study strategic concepts like weak squares, pawn structure, pawn majorities. This helps you to quickly identify what should be your plan even in a unfamiliar position.

If you have trouble winning a game that you should have won, study endgames. Specially, if you are ahead of material, try to simplify the position (trade pieces to give your opponent less chances to come back), and specially simplify into an endgame where you're sure you will win.

That depends on how good you are already. Beginners progress most by learning not to hang pieces. Up to the ~1000 elo level you will win by simply not blundering with little to no opening theory. After that the breadth of scope opens up a lot. I got to ~1750 over the board almost completely ignoring openings beyond move 4 or 5. Watching videos on strategy, how should I be arranging my pieces / where do they "belong", and simple tactics will take you far. Openings are important, I study them more now, but I wouldn't get bogged down by them. Picking up an intuition for analysing a position and it's thematic ideas is key.

Reached 1600 chess.com within a year starting from 600 and 2000 Lichess. What I believe to be more important is how you do something rather than what you do. What I mean is, someone can play many puzzles or games but if you are just blitzing out moves in puzzles even when you haven't calculated to a guaranteed advantage then you aren't learning anything. You are just exploiting what you have learnt over exploring by trying to look for patterns you wouldn't normally look for. Constantly even in complex positions people blitz out moves only to blunder.

This is why I don't recommend bullet to anyone.

I was a competitive chess player in my youth and am currently ~2300 on Lichess. Here are key aspects of any training regimen:

* Tactics - I did thousands of tactics puzzles using a program called CT-ART while under a time limit. I would have to complete 25 puzzles within 5 minutes while making 0 mistakes. If I made a mistake I would have to start from the beginning.

* Core positional concepts - Understanding pawn structure (double pawns, isolated pawns, passed pawns, pawn majorities, etc.), control of central squares, open files, king safety, and so on.

* Endgames - Many players neglect endgames. Master the basics: common rook-and-pawn and pawn-only endgames, how to checkmate with 2 bishops and bishop + knight, etc. Read Silman's Complete Endgame Course, Basic Chess Endings, and Dvoretsky's Endgame Manual (for advanced players) to improve your endgame play.

* Openings - Many people have mentioned learning openings, but it is generally a mistake for beginners and intermediate players to focus on this aspect of their game. It is not especially useful for a ~1000-rated OTB player to learn 15+ moves of theory in the King's Indian Defense only to end up in a position where there are slightly better according to theory but have no understanding of their position. It is better to center your opening repertoire around easy-to-learn openings and focus on improving other aspects of your game until you are strong enough to handle positions outside of opening theory.

Puzzles + learning openings. I highly recommend lichess for this

* train various endgames (undervalued) (e.g. Naroditsky’s videos on endgames: https://youtube.com/playlist?list=PLT1F2nOxLHOfQI_hFiDnnWj4l...)

* puzzles for tactics & mates

* learn 1 “easy to execute” opening for each color

I’m ~2000 online and got there by training tactics/puzzles and becoming really good at a few openings. I would suggest learning an opening or two for white and an opening or two for black. Kings Indian, modern defense, Sicilian defense, and danish gambit are some of my favorites.

I liked these tips: https://mbuffett.com/posts/chess_improvement_thoughts/

The trap to avoid is memorizing openings!

It takes a ton of time and brainpower, and doesn't make you a better player once you're outside your memorized moves..

Study and practicing openings. By this I mean you should memorise all the lines of an opening; not just the main lines. A vast majority of matches are won/lost within 30-35 moves by a few botched up opening moves.

I don't recommend puzzles that much. They give you mental satisfaction. However, it is one thing to think of a good move knowing before hand that there's such a move possible but entirely different to recognise that you are in such a situation in the middle of a game.