Is castling important?

Castling is a special move in the game of chess involving the king and either of the original rooks of the same color. It is the only move in chess (leaving aside promotion) that involves more than one piece of the same player. Castling consists of moving the king two squares towards a rook, then moving the rook onto the square over which the king crossed. Castling can only be done if the king has never moved, the rook involved has never moved, the king is not in check, and the king does not cross over or end on a square in which it would be in check. Castling is considered a king move (Hooper & Whyld 1992).

The notation for castling, in both the descriptive and the algebraic systems, is 0-0 with the kingside rook and 0-0-0 with the queenside rook. In PGN, O-O and O-O-O are used instead. Castling on the kingside is sometimes called castling short and castling on the queenside is called castling long; the difference being based on whether the rook moves a short distance (two squares) or a long distance (three squares) (Hooper & Whyld 1992).

Requirements

Castling is permissible only if all of the following conditions hold: (Schiller 2001:19)

1. The king must never have moved;
2. The chosen rook must never have moved;
3. There must be no pieces between the king and the chosen rook;
4. The king must not currently be in check.
5. The king must not pass through a square that is under attack by enemy pieces.
6. The king must not end up in check (true of any legal move).
7. The king and the chosen rook must be on the same rank.^[2]

It is a common mistake to think that the requirements for castling are even more stringent than the above. To clarify:

1. The king may have been in check previously, as long as it is not in check at the time of castling.
2. The rook involved in castling may be under attack.
3. The rook involved in castling may move over an attacked square (a situation possible only with queenside castling).

                                                           ------- from other websites(wiki).

 Strategy

Castling is an important goal in the early part of a game, because it serves two valuable purposes: it moves the king into a safer position away from the center of the board, and it moves the rook to a more active position in the center of the board (it is possible even to checkmate with castling).

The choice as to which side to castle often hinges on an assessment of the trade-off between king safety and activity of the rook. Kingside castling is generally slightly safer, because the king ends up closer to the edge of the board and all the pawns on the castled side are defended by the king. In queenside castling, the king is placed closer to the center and the pawn on the a-file is undefended; the king is thus often moved to the b-file to defend the a-pawn and to move the king away from the center of the board. In addition, queenside castling requires moving the queen; therefore, it may take slightly longer to achieve than kingside castling. On the other hand, queenside castling places the rook more effectively – on the central d-file. It is often immediately active, whereas with kingside castling a tempo may be required to move the rook to a more effective square.

It is common for both players to castle kingside, and rare for both players to castle queenside. If one player castles kingside and the other queenside, it is called opposite castling. Castling on opposite sides usually results in a fierce fight as both players' pawns are free to advance to attack the opposing king's castled position without exposing the player's own castled king. An example is the Dragon Variation of the Sicilian Defence.

If the king is forced to move before it has the opportunity to castle, the player may still wish to maneuver the king towards the edge of the board and the corresponding rook towards the center. When a player takes three or four moves to accomplish what castling would have accomplished in one move, it is sometimes called artificial castling, or castling by hand.

i do castle in more than 80% of my games. How much castling do you do? and how much importance yoou give to castling and why?

Of my last 10 games, I castled kingside 7 times, queenside twice, and didn't castle once.

No. Castling isn't important. Neither is winning.

Move two pieces for the price of one?  Protect my king and get a rook into play? 

I almost always castle, unless my opponent has other ideas. 

I tend to wait as long as possible before castling and may not castle at all if my opponent has castled and the waters are calm for fishing. Otherwise, if I like my position, opposite castling is awesome with a prediliction for the long castle to wake up the rook in a pawn free file.

Unless my opponent breaks (disrupts) his initial pawn line, I think castling is very important. The castling side depends on your plans. Else, I like very much to play with rooks (especially before the end of the middle game) and you are better off with the rooks on the sides (. . .provided your King is somehow safe. . .).

I tend to leave castling till late on and tend to like it if opponents castle early giving me a nice corner area to aim for which I occasionally achieve!(may change my tactics in future games!)

"Castle if you wish or because you must, don't castle simply because you can"

I think Beckyschess has given the "reason to be" of castling. "Felicitaciones" Becks 

 well,if u don't castle u are going to run into big time attacks...

I play chess for castling. If I don't, I get a losing sensation, unless not castling gives me an advantage.

how do you castle on chess.com

Unless you see a reason not to do so, always castle as it helps you connect your rooks and make the king safer. Now there are situation where it is okay not to castle. Usually in this type of position you have a mass of center covering your king and you usually have the bishop pair. Your action is on the wings. It could be also the center is locked up and the king is safe on the center. But as I told, unless you know what you are doing, always castle. A king sitting in open or semi open positions at middle game usually leads to disaster. It is very common for a good player to sac a pawn just to make his opponents king stay at the center and prevent castling in open or semi open positions.

1itachi - do you realize the only thing you needed to post were the last three sentences instead of a small book.  In the future, if you want more responses, you would be wise to NOT require a major effort of others to read your post!

In open games, castling is very important for both the safety of the King and to get the King's Rook into the game.  In closed games it is usually important, but you don't have to do it very early and often getting the King's Rook active is the main reason for doing it.

How often and when you castle depends on the opening you play.

For example, I play the French and King's Indian Defense as Black.

In the French, some lines involve early kingside castling, like the Closed Tarrasch.  Some involve frequent queenside castling, like the Advance with a3 and ...c4, or the Winawer.  Sometimes you don't castle at all, such as in certain lines of the MacCutcheon.  In a tournament game over the board I played Tuesday Night, I was on the Black side of a French MacCutcheon and my King moved to f8.  Often times castling is delayed, especially in lines where Black plays ...g5.

Compare that to the King's Indian Defense, and when's the last time you've played a King's Indian Defense as Black and not castled Kingside?  It typically early and automatic!

Take other openings, like in the KIA vs French, Black almost always castles on move 7.  In the KIA vs Sicilian, the early commitment to castling Kingside, in the structure with Black's Bishop on g7, Knights on e7 and c6, etc, is actually a mistake by Black and it should be delayed as long as possible.

In the Najdorf, Black rarely castles.

So just blindly trying to determine castling frequency and importance is useless.  A King's Indian player will tell you one thing, a Najdorf player will tell you something else.

A lot already said, and yes, of course castling is important.

I'll just give a personal point of view some people might find interesting.

I think of castling as something like a pawn move in the opening. In other words if you can make a useful developing move instead, or if you can prevent your opponent from some kind of ideal development move, then you'll usually prefer that to castling.

Usually you castle when there's somewhat of a lull in the opening sequence, where the next move isn't so critical... or you castle because you (or your opponent) is ready to open up the center and of course need your king to safety first.

Refer to Sultan Khan.....a gifted natural that often failed to castle , yet produced brilliances using that ploy.