How do you decide to castle on king side or on queen side? i know king side is castling is the quicker than queen side with just 4 steps.
Does queen side castling favours more on attack, than compared to king side (defense)??
For beginners there are some basic guidelines to castling. In general, choosing the right moment is as important as choosing the right side. Now, the guidelines I know of:
1) If you are playing white, it really depends on the position. Nevertheless, 99% of beginner-friendly opening lines work very well with white castling king-side.
2) If you are playing black, try not to castle before white does. If you do, white, which usually has the initiative in the opening, could attack your king and you will have no definite counter-attack point since white could decide to castle either side. Wait until white castles, and then go for the same side if you can.
3) If you gain some space or development advantage in the opening and your opponent castles before you do, think about castling on the opposite side (if center is open) or not castling at all (if center si closed). To this regard, become familiar with the technique of pawn-storm.
It strongly depends on the opening and the typical ideas related to that opening. (This is not surprising, as castling can actually be seen as a part of developing the pieces.) A typical example is the Yugoslav attack in the Sicilian Dragon, where the idea of the whole setup of white is to start an attack on the king side. Therefore, white castles on the queen side.
Yet, short castling is much more popular than long castling. The two main reasons are:
If pawns are more advanced on one side, or there is a material inequality to one side of your opponents pieces, castle opposite the majority of attack.
Typically, king side becomes favored, probably in part because of the property of castling you noted: that it's quicker to king side castle. Well, that and the King isn't as close to the center with King side castling.
Queen side castling is a bit easier to attack from however due to the imabalance of position (ie typically the other king is castled on its' king side).
Castling opposite sides often results in a race. All attack, no defense, fastest wins. The more time your opponent has wasted the more appealing starting this race gets.
If a file has been opened on the Kingside, say for example by trading your QB for the opponent's KN, then castling on that side might be dangerous. The same would be true on the Queenside. That's pretty simplistic of course. A feature of opposite side castling is that each side will mount an all-out attack on the King position using everything at his disposal, including the pawns. Generally the outcome will depend on "who gets there first with the most", so if you intentionally castle on the opposite side from your opponent, you must be prepared to attack aggressively. And as the other party answering this question has pointed out, castling Queenside leaves a broader pawn expanse in front of the King to defend. Typically an additional K move toward the corner is characteristic of castling Queenside, utilizing an additional tempo. If you haven't been playing that long, I would rely more on Kingside castling for a while as being quicker and safer. Then as you become more experienced you can begin to experiment with Queenside castling. x