I'm really a beginner in chess, and I just know the rules. So many times in the game I have no idea what should I do. None of my pieces are in danger and I don't have any strategies.
What should I do at this point? Make a worthless move, like moving a pawn? Try to make some space for my knights and bishops?
This is very hard to answer since the question is very broad, but in the opening, always ask yourself "what piece haven't I moved out yet?" If you move pieces twice or three times in the opening, and I am developing each one after only one move, soon you will be fighting with only two or three pieces against me with 5 or 6. You will not win that way.
Other than that, ask yourself what pieces of yours are not defended, and make sure they are safe; and conversely, look at what your opponent has that is undefended, and see if you can take advantage of that. Not losing pieces is the biggest problem for weak players.
Some typical things to look out for in the middle game in order to develop a plan... This assumes that it is a relatively quiet position without any imminent tactics that need to be taken care of first.
Advice I give to complete beginners is to place your pieces so that they point at your opponents king. Ignore any pieces and pawns between your pieces and the King. When playing against another beginner who has no plan this is a good strategy. This strategy has the benefit of helping learn about the power pieces exert across the board even when seemingly blocked.
When you understand the other advice given in the other answers than throw this advice away and use the better advice.
In my experience this is advice that beginners can understand. Unlike ideas such as the center is important which many find confusing at first. It is great to improve your worst piece, but how to you know which one that is? A beginner can understand get all of you're pieces out early, but much more experienced beginners have a difficult time doing that.
The general rule of thumb is improve the worst placed piece. I would be reluctant to move pawns without any purpose because you are likely to create a weakness. I would rather make a do nothing move, it is often could be a rook move on a back rank, as long as it really doesn't do anything; this move you can always "undo" (unlike the pawn moves!).
Wrong plan is often better than no plan, try to come up at least with something.
And after the game, make sure to go back and study the position.
Note: everything I'm saying is assuming you're playing white. Everything is also true for black, you just have to reverse the rank numbers. I'm also using algebraic notation; if you're unfamiliar there are a lot of resources.
In the opening, your goal should be to control the center with pawns (if your opponent lets you, play d4 and e4 as your first moves), get your bishops and knights developed, castle, and finally develop your queen. After you do all of this, your rooks will be "connected", meaning they're both on your back rank and protect each other, and are ready to slide over to good files.
If you're in an opening and don't know what to do, refer to this checklist. If you have an undeveloped bishop or knight, develop it, even if you don't have a specific plan for it. Getting knights to c3 and f3 is common, especially Nf3 (in many lines, a knight on c3 blocks the c-pawn, so either you play c4 first, or you develop that knight to d2 instead).
The game transitions to the middle game when both of you have done at least most of this. During the middle game, you may be fighting for control over the center, and trying to engineer advantageous trades, either by tactics that win material, or by trading a bad piece of yours for a good piece of theirs.
If you're in a middle game and don't know what to do, here's a checklist of ideas:
b2 can be deadly). If you don't have a plan, simply putting a piece on a good square is a good thing to do.d1, your opponent has moved a rook to d8, and there are a bunch of pieces in the middle. If there's a big melee and all of those pieces in the middle get cleared out, your opponent might end up with a clear shot at your queen. So maybe a good move is to move the queen somewhere else.And of course, you have to think of all of these things from your opponent's perspective too.
The game transitions to the endgame once a lot of material has been traded down. Endgames vary wildly and I'm not sure how much general advice I can give briefly. If the endgame has equal (or nearly equal) material, it's common that the strategy is to try to promote a pawn (while keeping your opponent from doing so). You have to try to get a passed pawn, a pawn that can't be attacked by opposing pawns any more, and then escort it to glory.
If you have more pieces left than your opponent, it's often advantageous to trade down. For example, if you have a rook and a bishop and your opponent has only a bishop, trading the bishops may make winning easier. With more pieces on the board, you might be vulnerable to tactics, but your opponent won't have any tactics if he doesn't have any pieces!
If you have fewer pieces than your opponent, then you probably have to try to fight for a draw. In general, one way to do this is to try to take all of their pawns so they can't promote. For example, if your opponent has a bishop and some pawns, and you only have pawns, he will probably be able to use that bishop to help promote a pawn. But if you can manage to trade off all of the pawns, then a king-bishop vs. king endgame is a draw.
Make a worthless move, like moving a pawn?
Careful! Pawn moves can have extreme consequences. Every time you move a pawn, you're undefending squares. For example, consider the common structure where White has castled kingside and still has the pawns on f2, g2, and h2. Sometimes we have to play g3 for defense, but after that, Black can put a piece on f3 or h3 and it can't be attacked.
The tip I learned from Jeremy Silman's "Reassess your chess" series was that, if you can't find a weakness in the opponent's position, you should actively be trying to create a weakness.
For example, in closed positions it happens pretty often that all your pieces are developed and in "good" positions, but you still have no attack. When this happens, you should look at the position and ask yourself what sorts of weaknesses you could create. Can you push some pawns to reduce your opponent's space? Does their pawn structure have any potential weak points you could put pressure on? Can you lock their minor pieces in? How quickly can you open up the center or the flanks for an attack? The answers to these questions will determine what you should do next.
The strategy is a very deep concept which requires creativity and understanding. It is important to understand the mechanics of certain types of positions and this can be achieved by looking at different varieties of top grandmaster games especially ones where the players have a different type of style. Sometimes even then you have to look at the tiny details in the position and come up with ways in which to play to take advantage of them. Savielly Tartakower once said "Tactics is knowing what to do when there is something to do. Strategy is knowing what to do when there is nothing to do".
Study more and play less.
Learn about pawn structure. Play over GM games to see what they do. Some common ideas may occur to you to try.
Look for weaknesses you can attack.
Look for your weaknesses you could defend better.
Can you attack the king? Can you expand for space? Can you put pieces on squares with more mobility closer to the enemy? Can you set up a tactical position to win material?
Do not move pawns without a reason. Do not make worthless moves unless you are in zugzwang.
Study positional play for more ideas on what to do in quiet positions like you describe.
This answer is a little indirect but it helped my wife get a better grasp of chess and now no longer sees any board state as just a bunch of useless moves.
If you have someone you play with regularly ask them to give you a handicap by verbalizing what they are thinking on their move.
-ex: "I can move my pawn up two getting control of the center, putting pressure on your knight and rook... But then your knight could fork my queen and rook... I have two pieces putting pressure on your center pawn and if I get another in position I could make a beneficial exchange... That bishop on the left hand side is not defended and could be taken advantage of..."
During your turn, the opponent doesn't speak, allowing you to form your own strategy and build your skills.
Essentially their strategy becomes an open book for you to look through which also makes for a more competitive game between the two of you. I find (as the more experienced player) playing passively (not to your fullest) teaches little to nothing to the new player while playing with your true skill makes for a one sided game that no one has fun with.
Seeing what goes through a better chess players mind will help you figure out what you should be looking for or thinking about on your turn.
In the beginning you can ask questions to understand the opponents statements but once you start understanding them, just sit back and absorb.
I'm by far not a good chess player (compared to most regular players) but being the open book opponent it also helped me with my game.
The general key points/pointers found in other answers here, should with time be revealed to you as you play more games in this format. I think you'll have a better grasp of them when you see them in action / being used by your opponent and what position it then puts you in.
(Note: only works with an honest player who will blurt out every single thought that goes through their mind. No pre-processing / filtering. Every move considered and eventually discarded is useful information to a new player)
Start reading some books for beginners such as those by Seirawan. The idea is simply that the author will often explain the rationale behind a move in the book, and just by reading those you will be exposed to tactical and strategic motifs that you will see occurring in your own games.
Also, reserve a little time during your study hours for solving puzzles. Websites such as chess.com has a good variety of puzzles for beginners, and the puzzles will gradually become more difficult as you become more adept at solving those. The idea here is that you will start to see patterns in your own games similar to what you saw in the puzzles, and this will give you more ideas on the board.
If you look at a position and find yourself saying, "None of my pieces are in danger and there is nothing to do", you should consider you are probably missing something. Most chess positions are not so safe there is nothing that can be improved. A lot of the time there is something urgent that needs fixing, or an opportunity to take something from your opponent. But it is hard to learn to see these things.
My suggestion is to get practice evaluating positions by studying the puzzles on Lichess. They are drawn from real-world games so they look like positions you will see in real life. A lot of these may look perfectly quiet but there is a tactic that wins an exchange, picks up a piece, or just mates. Working through some of these should give you a new awareness of things to look out for.
Since you say "I just know the rules", try going through the Chess basics section on Lichess as well to see if you are missing anything, it is a very thorough introduction that covers basic tactics.
When playing against other beginners, basic chess tactics are very effective — and a lot of fun.
If you don’t know about discovered attacks, pins, skewers, and forks, learn about them.
Winning Chess Tactics by Seirawan is a great resource.
Focus on attacking the king when you can. Beginners’ defenses are weak enough that is usually the quickest route to victory.
More advanced players may attack the weakest piece, but save that concept for later in your chess development.
For the first few moves, learning and following well-established openings is the best plan.
There are lots of online resources for this. Just google: chess openings
