Development is key to the opening. The objective is to place your pieces on optimum squares. This means pawns controlling the centre, along with the knights and bishops. You should then proceed to castle by the 10th move. Notice I haven't talked about your queen. The queen should be one of the last pieces you move (unless there is a good reason not to) - the queen is too precious to be thrown out in the frontline, as it will give your opponent a chance to develop their pieces with tempo. Remember that 'Knights on the rim are dim.'
That was quite a dramatic example of what to do and what not to do. Black has not developed a single piece whereas white's pieces are on their optimal squares. Both pawns control the centre and white's bishops and knights are controlling the centre.
This is a famous game played by Morphy. Notice how black's pieces were not developed (e.g. black's knight and bishop were undeveloped due to their queen. Furthermore, black could not castle, and therefore his king was not safe. Morphy had a clear advantage throughout the game due to always being a couple moves ahead and maintaining constant pressure on black's side.
This game included a similar pattern to Morphy's. White had a huge advantage on development and black's king was unprotected. White used a clever queen sac to win the game.