Here is a sort of strategy guide, since some people are saying their girlfriends are beating them at chess, which is an abomination.
There are three phases of a chess game, beginning, middle, an end game (for global domination, no j/k).
The beginning is all about understanding different openings. When you hear things like Ruy Lopez, or Sicilian, or French Defense, these are types of openings that have been worked out for over 200 years, so there is a definite theory going on with these openings. The easiest way to learn openings is to get a chess engine and type in some simple moves. This way the chess engine just tells you what the best move order is. If you are a new player, don't ever play the Rook pawn forward, a lot of beginners do this and it's a terrible opening. The best openings are either playing the king or queen pawns forward.
The first 4-8 moves are generally considered the Beginning. Strive to achieve a 'perfect position'
Note where the white pieces are, this is the 'ideal position.' This position is never achieved in normal games, and is not even realistically a good opening, but it is an ideal which to base where pieces are supposed to go. Take note of the knights, these are ideal homes for the knights in most chess games. Rooks right in the middle are great spots, and bishops operating somewhere along those diagonals.
The Middle Game
The middle game is clearly the most confusing and complex part of a chess match. It is where there are literally millions of different combinations, and so not even Grand Masters can predict with accuracy what will come about. I define the middle game as being when both sides have developed most of their pieces and when there is an imbalance of at least one pawn. The opening/beginning of chess usually involves a fight for one pawn. Some openings willingly give up a pawn, which is called a Gambit opening. Once you are in the middle game, I like to subdivide this into 3 more phases of beginning, middle, and end.
The Beginning-Middle.
After the sides are drawn, the goal here is to try and win some material from your opponent. Take note of deficiencies in your enemy ranks, such as
doubled pawns (where one pawn is in front of the other, which prevents the pawn in behind from moving),
Holes - a very important term in chess, a square that cannot be attacked by your opponent's pawn. You are supposed to put your knight and bishops in these holes.
Uncastled Kings - When you prevent your opponent from castling, this puts the king in a dangerous position.
Open files - where either your pawn or your opponent's pawn is cleared from a column so that it is open and unobstructed, this is where you want to place your rooks.
In case you don't know, this is the point system in chess
Pawn - 1 point
Knight/Bishop - 3 points
Rook - 5 points
Queen - 9 points.
King - considered infinity points.
So if at all possible, you will want to exchange one of your knights or bishops (3 points) for your enemy's rook (5 points). This puts you at an advantage. Once you have that advantage, you move to the next phase of chess.
The Middle-Middle game.
If you have a clear advantage, it is a mathematical certainty that you will eventually win if you play your pieces correctly. Overpower them because you have the advantage. Use these chess tactics to crush your opponent
Pin - When your opponent can't move a piece because otherwise you'd be able to capture his king. This is a pin where it is illegal for your opponent to move. Another pin is where if your opponent moves their piece, their queen or rook would get captured, this is a legal pin but one they would not want to do.
Fork - Where one piece attacks two pieces simultaneously, knights are best known for doing this, but all pieces can do it.
Revealed checks - If your rook is lined up with your opponent's king, and you move your knight, the rook then puts the other king in check. So your check was revealed, this can lead to deadly results.
Some of these moves are so deadly I call them 'game ending moves' where your opponent immediately resigns because it does too much damage to their side. Capturing their queen, for instance. Once this is done, you are moving towards the end game.
End of the Middle Game.
The end game is technically when the queens are off the board. The strategy here is to figure out how to promote one of your pawns to be a new queen. So before you trade off the queens, make sure you have a clear idea of how to promote your pawns. If you only have a one or two pawn advantage, it may not be a guaranteed victory, so plan out the end game before this happens.
End Game
End games involve a lot of calculation but with less pieces, so it basically involves counting how many squares you need to get a pawn promoted to a queen. Grand Masters can calculate a lot of moves ahead in the end game, many more than in the middle game. In the end game, your King becomes the star player. Earlier in the game, the king's job is to hide and be protected, but in the end game, you have to play your king as he becomes your most powerful piece. His job is to help the pawns get to the end of the board so they can be promoted (usually to a queen but they can be promoted to a rook, knight, or bishop, some scenarios make this necessary). Rooks are also powerful in the end game, as they can block off the king. A king can't occupy a row or column a rook is guarding, so it cuts off the king completely.
Checkmate.
Once you have an extra queen, or a rook up on your opponent, it is time to check mate their king. The easiest method is to do the step ladder approach, where you funnel the king to the edge of the board with two rooks or a rook and a queen, and you end up with something like this
The next move of white is to take the bishop and that is checkmate. King and queen checkmate is also common.
