White Alain C. The White King in Chess Strategy

Hippocrene Books, 1973. — 212 p. — ISBN 978-0-88254-036-X.Introduction to Chess Strategy: The King
As the king is the most important piece, it's vital that you know what to do with him. The more pieces there are on the board, the less safe the king becomes. It is especially dangerous for the king when the enemy queen is still on the board. When discussing the king's role in chess strategy, we are mostly interested in how to keep him safe from attack. Only in the endgame, when there are few pieces left on the board, is it safe for the king to emerge from his fortress and join in the attack, but we will look at the role of the king in endgames in a later tutorial.Castle early
One of the most important things to remember early in the game, is to castle your king to safety in the corner. You may be wondering why it is so much safer for the king in the corner than in the centre - after all, isn't he more likely to get trapped in a corner? Well, sometimes, but the big reason to get the king out of the centre of the board is because the centre is where most of the action occurs. The centre in chess is the high ground. Occupying it confers a strategic advantage, and both sides should be fighting to control it for themselves and deny it to the enemy. The central pawns need to move to let out the pieces and fight for control of the centre, and they are often exchanged off, leaving the central files open. The king is far too vulnerable to be left in the middle of this battle.