Time is a very important element of chess. The player whose men are ready for action sooner will be able to control the course of the game. If you want to be that player, you have to develop your men efficiently to powerful posts.
Many inexperienced players like to move a lot of pawns at the beginning of the game to control space on the chessboard. But you can't win with pawns alone! Since knights, bishops, rooks, and queens can move farther than pawns and threaten more distant targets, it's a good idea to bring them out soon, after you've moved enough pawns to guarantee that your stronger pieces won't be chased back by your opponent's pawns. After all the other pieces are developed, it's easier to see what pawns you should move to fit in with your plans.
It's tempting to bring the queen out very early, because it's the most powerful piece. But your opponent can chase your queen back by threatening it with less valuable pieces. Look at Example A: after 1. . . . Nf6, black threatens to drive the white queen away with either 2. . . . Nd4 or 2. . . . d6 and 3. . . . Bg4.
Instead of just moving pieces out, try to determine the best square for each piece and bring it there in as few moves as possible. This may save you from wasting moves later in the game.