1) Control as much of the board as possible. Space is always a good thing because you have more room to maneuver your pieces in.
2) Develop the attacking pieces to good squares where they will help you in the game.
3) Do this as quickly as possible. Imagine it as a race: the first one to get to the center of the board controls it.
4) Avoid moving the same piece twice, unless absolutely necessary, during the opening. Remember the "race" - try to save moves.
5) For a beginner I would recommend they start the game with the move 1. e4 or 1. d4. These are by far the most common moves and the ideas are easy to pick up. See the articles Survey of Chess Openings and Comparison Between e4 and d4.
6) Knights belong in the board's center. This is because they control more squares here than on the rim. "A knight on the rim is dim" is a common chess phrase, and it is especially true during the opening.
7) Trying to attack with the queen early in the game is usually a bad idea. Your opponent will be able to attack it with less valuable, protected pieces, which will force you to move your queen again and again, preventing you from developing the rest of your pieces, while your opponent develops his or hers.
8) After you have developed your bishops and knights, you should castle. Castling helps protect your king, and brings a rook towards the center of the board for to help in the fight.
9) The f2 and f7 square's are, in the beginning of the game, weak spots. This is because the only piece defending these squares is the king. Only two pieces are needed to be attacking this square to threaten to capture. Games are lost all the time by players forgetting about this square.
The result of most chess is decided in the middlegame, and some players will emphasize this to the extent of putting almost no study at all into the opening. This is a dangerous approach, however, as to get to the middlegame, the opening has to be passed. Why would anyone want to reach a middlegame, armed with all the knowledge to beat a player rated several hundred points above themselves, in a terrible position? This can be avoided by learning the basic opening principles which I will explain here.