It's a skill that you have to constantly work on, I've been developing some guidelines for myself:
1). Look at all checks. That will take care of any elementary forks.
2). Look at all captures, and imagine the position after any captures. Often this will help you identify removal of the guard tactics or attraction. Make sure to pay attention even to captures that lose material on the first move (sac the exchange, etc...).
3). Notice any undefended pieces (or pawns) that the opponent has. If you threaten an undefended piece, that is a very forcing move. It's like a mini check - the opponent must react or else they will lose that piece. If you threaten 2 undefended pieces at the same time, guess what - that's a fork. If you can't see a fork right away, but notice the undefended pieces, that might help you find the fork. Sometimes a Knight can jump to attack an undefended piece, and then use that tempo jump to attack a real fork like on f2/f7/c2/c7. Sometimes you can "create" an undefended piece with a pin. For example, imagine an outpost knight on d4, a pawn on e5 and a King on e8. If you put a rook on e1, that pawn is no longer defending the knight on d4. The opponent may not react to this right away, since you're not threatening the knight right away. But in their mind, the knight is often defended. Then look for ways to combine an attack on that knight with an attack on something else.
4). Look at pawn attacks or attacks on a piece with lesser value. Similar to #3 - if you attack a piece with a piece of lesser value, that's like a mini-check. Opponent must react or else they lose material. The way they react may lead to a removal of the guard tactic (deflection), or some other tactic (like a discovered attack).
5). Find ways to create mate threats. For example if you have a bishop staring at f7, you can make a queen move that attacks f7 and also attacks something else that's undefended or unprotected, that again is like a fork. Attacking a square that you can mate on is also like a mini-check.
6). Work on noticing alignment patterns. Anytime you have pieces lined up on a diagonal or a file - opportunity for skewers, pins, discovered attacks.
7). Put bishops and rooks facing the opponents king or queen, even if there are pieces and pawns in the way.
- Harder to spot are pieces that have potential of getting trapped. #4 may help in that.
- Also pay attention to the backrank. Sometimes you can pin pieces with a rook or queen across any backrank square.
- Practice checkmate patterns because if you identify a mating square, you can combine that with other ideas (see #5). Threatening a mating square is like a mini-check.
It's a skill that you have to constantly work on, I've been developing some guidelines for myself:
1). Look at all checks. That will take care of any elementary forks.
2). Look at all captures, and imagine the position after any captures. Often this will help you identify removal of the guard tactics or attraction. Make sure to pay attention even to captures that lose material on the first move (sac the exchange, etc...).
3). Notice any undefended pieces (or pawns) that the opponent has. If you threaten an undefended piece, that is a very forcing move. It's like a mini check - the opponent must react or else they will lose that piece. If you threaten 2 undefended pieces at the same time, guess what - that's a fork. If you can't see a fork right away, but notice the undefended pieces, that might help you find the fork. Sometimes a Knight can jump to attack an undefended piece, and then use that tempo jump to attack a real fork like on f2/f7/c2/c7. Sometimes you can "create" an undefended piece with a pin. For example, imagine an outpost knight on d4, a pawn on e5 and a King on e8. If you put a rook on e1, that pawn is no longer defending the knight on d4. The opponent may not react to this right away, since you're not threatening the knight right away. But in their mind, the knight is often defended. Then look for ways to combine an attack on that knight with an attack on something else.
4). Look at pawn attacks or attacks on a piece with lesser value. Similar to #3 - if you attack a piece with a piece of lesser value, that's like a mini-check. Opponent must react or else they lose material. The way they react may lead to a removal of the guard tactic (deflection), or some other tactic (like a discovered attack).
5). Find ways to create mate threats. For example if you have a bishop staring at f7, you can make a queen move that attacks f7 and also attacks something else that's undefended or unprotected, that again is like a fork. Attacking a square that you can mate on is also like a mini-check.
6). Work on noticing alignment patterns. Anytime you have pieces lined up on a diagonal or a file - opportunity for skewers, pins, discovered attacks.
7). Put bishops and rooks facing the opponents king or queen, even if there are pieces and pawns in the way.
- Harder to spot are pieces that have potential of getting trapped. #4 may help in that.
- Also pay attention to the backrank. Sometimes you can pin pieces with a rook or queen across any backrank square.
- Practice checkmate patterns because if you identify a mating square, you can combine that with other ideas (see #5). Threatening a mating square is like a mini-check.