Queen
From WikiChess
The queen is the most powerful, and one of the most useful chess pieces. It can move diagonally or orthogonally in any direction, combining the powers of the rook and bishop. With a correctly placed board, the white queen begins on d1 and the black queen on d8. An easy way for beginners to remember this, the Queen always starts on her own color. The white Queen on a white square, and black on black. It is worth 9 points of material and is usually represented by a Q in English algebraic notation.
[edit] Strategy
Many novice players will want to bring out their queens early on in the game; while this strategy can be effective against other beginners, experienced players know how to make use of their queen better. Due to its long range and flexibility in movement, the queen is a great piece to execute forks with, though this is usually only useful if both threatened pieces are undefended or one is a king (in check) and the other is undefended. A queen is at her most power when the board is open, and the opponent's king and other pieces are undefended. Because a queen is so powerful, it is not a good idea to trade it for an opponent's piece, unless it is a queen, or doing so guarantees a checkmate.
