At the very beginning of a chess game, both players compete in a process called development. The process of development comprises three main tasks:
- Moving all pieces to their most advantageous squares.
- Occupying and attacking (controlling) centre squares. These are: e4, e5, d4, and d5.
- Hindering the opponent's development without wasting moves (tempi).
Being ahead in development is the aim of the opening. An advanced player can easily convert a lead in development into a larger advantage by way of attack or combination. It is therefore that the process of development is about being efficient. In order for a campaign of development to be successful, it must adhere to several laws which can be discerned from the works of Wilhelm Steinitz, Siegbert Tarrasch, and Aron Nimzowitsch:
- Each piece must be moved only once during the opening.
- Pawn moves are made only to control centre squares, open lines for pieces, or attack more valuable enemy pieces.
- Pieces must not be placed where they can be attacked by less valuable pieces.
- Develop first the pieces which have fewer options or a certain home.
- Consider the King's safety at all times.
An advantage in development 
An advantage in development is quite easy to spot - you will have more pieces out than your opponent. When possible, try to combine attack and development; try to develop with gain of time. For example, after the moves 1.e4 e5 2.Nf3, White has attacked the e5-pawn, forcing Black to defend it. Of course, Black could easily defend the pawn with 2....d6, but this doesn't develop a piece. Black's best moves here are either 2....Nc6, developing and defending, or 2....Nf6, developing and attacking the e4-pawn. An advantage in development, all other things being equal, is an advantage, as you have more pieces out that can easily attack an uncastled king. An important thing to remember about development is that it is a dynamic advantage, that is, if you do not use it immediately it will evaporate. This fits in nicely with Steinitz's first law of strategy.
Most of the time, gambits are sacrifices to gain a lead in development. One example of a gambit to gain time to develop pieces is the Danish Gambit, where White quickly develops his bishops, which can expertly use the open diagonals of the board. 1.e4 e5 2.d4 exd4 3.c3 dxc3 4.Bc4 cxb2 5.Bxb2. White has received an enormous lead in development for his two pawn investment. In this position, Black will try to exploit his material advantage while bringing out his pieces, while White will aim for a quick attack that will prove the validity of his lead in development. Black can play a countergambit, a sacrifice of one of his pawns to equalize in development. Black normally plays in this position the countergambit 5....d5!, giving up one of his extra pawns to gain time on the White bishop. 6.Bxd5 Nf6 and White has nothing better than 7.Bxf7+ Kxf7! 8.Qxd8 Bb4+ =/=
Sound or not? 
The great master, Steinitz, once said: "The only way to refute a gambit is to accept it." Some gambits don't aim for a lead in development. For example, the Smith-Morra Gambit in the Sicilian Defense goes 1.e4 c5 2.d4 cxd4 3.c3 dxc3 4.Nxc3. This gambit is considered unsound at master level. Although White gets a lead in development, in this case Black expects to eventually catch up. The main reason for this pawn sacrifice was to gain the open c- and d-files for White. Gambits of this nature are considered unsound because of the abstract nature of the advantage; it is disputed whether the open lines are enough for the sacrifice.
What to do if your opponent has a lead in development 
If your opponent has a lead in development, the most important thing to do is to get your king safely castled. Remember that if the opponent has a lead in development, he can open lines--right up to your king. That's not good, because open lines to your king mean that pieces can easily get to him, and easy access to the king means mate sooner or later. After the king is safely tucked away in a corner, your next objective is to get out the rest of your pieces. This will refute the pawn sacrifice. The final step is to keep your material advantage until the endgame, or use the extra material to attack the opponent's king.
What to do with a lead in development 
Shopron, 1934 Position after White's 12th move
Now you have the advantage! Here are the priorities for you, in no particular order:
- Open lines to the enemy king. If you do this, the king becomes a sitting duck in the center of the board.
- Keep the opponent's king in the center. The center is normally where all the action takes place, and it is not particularly safe to keep the king where the action is. Also, a centralized king blocks communication from the pieces, which suffer from a lack of coordination.
- After both of the above are accomplished, try to either mate the king or regain your lost material.
All of these actually make sense, because if your opponent's king is stuck in the center, open lines are like highways leading to the king! The game at right, Grünfeld--Spielmann, went from here 12....e5! 13.fxe5 Nxe5!! 14.dxe5 d4! 15.Nd1 Bxe5. At the cost of a knight, Black has opened up lines in the center. He now has a clear advantage because, despite his piece deficit, the king is wide open and White's pieces are uncoordinated. 16.e4!? Bxe4 17.Nf2 Bd5 18.Qh3 Qe7 19.Be2 d3! The center has been destroyed and White's king loses the game for him. White resigns on move 34 (...Bxe1).
- Alburt, Lev and Palatnik, Semyon. The King in Jeopardy, rev. ed. New York, NY: Chess Information Research Center, 2001.
- Capablanca, Jose Raul. Chess Fundamentals. New York, NY: Harcourt, Brace & World, 1921.
- Silman, Jeremy. The Amateur's Mind, 1st ed. Los Angeles, CA: Siles Press, 1999.