Basic Principles: The Queen

The queen is a very valuable piece to have, but it can also become a liability.  Since the queen has so many places it can move, it is very easy to believe that your queen is protecting several of your pieces and attacking many points on the board.  Be very careful not to "overload" your queen like this, or your opponent can "pull the rug out" by (for example) trading a piece, which then leaves other pieces hanging, or dismantles your attack.  In this example, white gains a knight by taking black's rook.  When black's queen takes back, white's queen can now take the knight for free.

One of the biggest mistakes the average player makes in chess is bringing out the queen at the beginning of the game (known as the "terrorist attack")  This may be fine against another average opponent, but when your opponent knows what he is doing, you will end up spending a lot of time trying to maneuver your queen while he is gaining a much better position.  Another problem with putting the queen out early is that it becomes a liability.  It will either be in a spot where your opponent can bring out new pieces to attack it (in which case you almost always end up having to move it) or it will be in the way of your being able to bring out one of your pieces to a good spot.

Keep in mind that a good player can play without his queen.  I cannot overemphasize how important it is to be able to play good chess without having your queen.  If you get good at using your other pieces without the queen, you will already be a step ahead of the competition.  If you do not, then your opponent will be able to make you waste time moving your queen out of the place where you wanted it to be because you are reluctant to trade, and then eventually he will force the trade when it suits him.