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
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
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
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:
- Take inventory of the pieces trying to control the middle and see if you can improve there. Maybe your opponent has a center pawn that he's defending twice, and you're attacking twice. Can you attack it again? This is one of the most basic tactics to keep track of: number of attackers vs. number of defenders. If you have more attackers, then you can trade everything down and end up on top (maybe--if one of those attackers is your queen, then you don't want to lose that in the melee). A LOT of middle game tactics at the high level just boil down to this, with more advanced ideas like overworked pieces or removing the defender.
- Look for tactics. Can you employ a fork, pin, skewer, etc? Even if you don't have one of those maneuvers cleanly, can you at least move towards threatening something like that, forcing your opponent to use moves to defend?
- Simply improve pieces. Rooks on your back rank love to be on files where you don't have a pawn (open or half-open files). Knights love to be on outposts, which are squares that are forward in the position (4th rank or further), defended by a pawn, and unattackable by an opposing pawn. Bishops love to be on long diagonals, meaning that they're somewhere safe on your side but pointing across the board at important things (if Black has castled kingside, a bishop on
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.
- Trade off your bad pieces for their good pieces. Does your opponent have a killer bishop like I described above? Do you have a knight that you don't know what to do with? Trade them!
- Do you have major pieces (rooks, queen, king) that are aligned with your opponent's pieces? Maybe your queen is still on its starting square
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
h2. Sometimes we have to play
g3 for defense, but after that, Black can put a piece on
h3 and it can't be attacked.