The king in a game of chess has the option of castling on both the sides of the board even though most of the time, castling is preferred on the kingside. 

This is so because just two pieces, the knight and the bishop stand between the king and the rook and it is faster to castle, while on the queenside three pieces have to move out before the king can castle.
Many a time a player delays castling and fools his opponent by inviting an attack and then castling on the opposite side.

In the game which follows, black delays castling while white moves his queen deeper into enemy territory on the king side.

Black then suddenly castles on the queen side and white's queen which had moved solo into the enemy territory finds herself targeted.

Black then drives away the queen and also launches a winning attack, underlining the importance of timing in employing the castling method.

White: Albert Riemens (2180) – Black: Richard Meulders (2265)
Antwerp, 1996

Sicilian Defence
1.e4 c5
The Sicilian Defence
2.c3
The slow Sicilian.
2. ..d5
Black is more keen on settling matters at the center rather than white.
3.exd5 Qxd5 4.d4
White has to play this move rather earlier than he thought
4. ..e6 5.Nf3 Nc6 6.Na3 Nf6 7.Be3 cxd4 8.Nb5
Threatening the fork 9.Nc7
8. ..Qd8
Back to square one! If [8...Qd7 9.Nbxd4 Nd5 10.Bb5 Nxe3 11.fxe3 Qc7 12.Ba4 Be7 13.Nxc6 bxc6 14.Nd4 0–0 15.Qf3 (15.Nxc6 Bd6) 15...Rb8 16.0–0–0 Bb7 17.Bc2 g6 with a very slight edge for black
9.Nbxd4 Nd5
Black could have developed with 9...Be7 10.Nxc6 bxc6 11.Qa4 Bb7 12.Rd1 Qc8 13.Be2 0–0 14.0–0 Nd5 15.Bg5 Bxg5 16.Nxg5 h6 17.Nf3 c5 18.Qh4 Qc7 with more or less an equal position
10.Bg5
If 10.Bd2 Nxd4 11.Nxd4 Bc5
10...f6
Ruling out castling on the king side. Worth a look is 10...Be7
11.Bh4 Be7 12.Bb5 Bd7 13.0–0
White decides to castle on the king side well aware that black may not castle on the king side and launch an attack.
13. ..Nxd4 14.Nxd4 Nc7
If 14...Bxb5 15.Nxe6! Qd7 (15...Qd6 16.Nxg7+ Kf8 17.Nf5 with advantage for White) 16.Re1
15.Re1
White had a better option in 15.Bd3 0–0 16.Qh5 f5 17.Bxe7 Qxe7 18.Rfe1 Qf6 19.Nf3 and if  15.Bc4 e5 16.Re1 exd4 17.Qh5+ g6 18.Qh6 with advantage for White
15...Nxb5
The position becomes a bit unclear here.
16.Nxb5 Qb6
A good move. If he hurries with16...g5 17.Qh5+ Kf8 18.Nd4 gxh4 19.Rxe6 white then gets an edge
17.Nd4 e5 18.Qh5+ g6 19.Qh6

Diagram 1
19. ..0–0–0
Black finally castles on the queen side just as he had planned all along.
White's intention of attacking with his queen fizzles out 
20.Qg7
Getting deeper into enemy territory
20. ..Rhe8 21.Qf7
Resisting the temptation to grab the pawn as 21.Qxh7 exd4 22.Rxe7 Rh8
21...g5 22.Bg3 h5 23.h4
If 23.f4 gxf4 24.Bxf4 Bd6 black gets advantage
23...gxh4 24.Bxh4 Bc5 25.Nb3 Be6
Black's pieces start getting stronger and occupy strategic squares
26.Qxf6
If 26.Qxh5?? Rh8 and if 26.Qh7
26...Rf8 27.Qxe5 Bxf2+ 28.Bxf2
White would have offered better defence with 28.Kh2 Bxb3 (28...Bxh4 29.Qxe6+) 29.Bxf2 Rxf2 30.axb3 Rg8 31.Rg1 (31.Kh1 Rfxg2 32.Qf5+ Kb8 33.Qe5+ Kc8 (33...Ka8 34.Qe8+) 34.Qf5+) 31...Qc6
28...Qxf2+
Getting too close for comfort to the King
29.Kh1
Once again a mistake. He should have played 29.Kh2
29...Bd5
The finishing touch! White resigned as there is no escape and the King will soon be dragged forcibly into a checkmating net.

Diagram 2
Black to play and win
1... Qd1+ 2.Kxd1 Bg4+ 3.Ke1 Rd1 check-mate
Manisha Mohite