While the number of possible openings in chess is simply so wide and numerous that it is almost impossible to memorize every single line (and I do NOT recommend brute-force memorization of opening lines without first getting to understand the plans behind them!), the basic idea behind any opening is the same: To mobilize one's forces and attain a lead in development so that one has an advantage in the middlegame. As such, here are 4 simple but important tips which we should all be familiar with if we wish to do well in the early stages of the game:
1. Pay close attention to your development and tempo
The most fundamental idea in the opening; at the start of the game both armies mobilize their forces for the upcoming assault. If one is able to gain a lead in development and tempo it allows him/her to seize the initiative and possibly launch an attack first before his opponent is able to fully consolidate himself.
Point 1 can be further divided into 4 further subpoints:
(a) Develop all your pieces
I don't think this really needs elaboration.
(b) Try not to move each piece multiple times in the opening
The idea in the opening is to mobilize ALL your pieces; moving pieces multiple times without any good reason only serves to slow down your development. As quoted by Aaron Nimzowitsch in "My System": "How undemocratic for instance, it would be to let one of your officers go for a long walking tour, while the others kicked their heels together at home and bored themselves horribly. No, let each officer make one move only, and... dig himself in."
(c) Don't push pawns unless it aids you in your development/ slows down the opponent's development.
Similar to the idea in (c); pushing pawns unnecessarily only wastes precious time which you could have used to develop your pieces. The only times which you should push pawns are when it helps clear the way for your pieces to develop (e.g. pushing the centre pawns in the opening) or as a prophylaxis against possible enemy incursions (e.g. a timely h3/h6 to prevent the annoying bishop pin on g4/g5)
(d) Try to develop pieces and make threats at the same time if possible
If you can slow down your opponent's development so that you can gain a lead, why not? I have included a good example of this in the sample game at the end of this article.
2. Do not exchange unnecessarily
This is a very common mistake among beginners; I have seen too many games where young kids mindlessly exchange pieces, not realizing it only helps their opponent improve his/her position. This is especially true for the opening where pieces are just being developed and their relative strengths are just being ascertained.
One simple example will the position after 1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Nf6 5. Bg5 d6:
|Position after 5... d6|
White's bishop pins the knight, and now 6. Bxf6?! is questionable since after 6... Qxf6 Black retakes and develops his Queen at the same time. A fine case of exchanging without thinking!
This rule is a very simple one that we all should have committed to memory, yet it gets flouted every day by so many amateur players.
3. Try to control, if not occupy, the centre
In the early stages of the game it is good practice to stake a claim to the centre of the board (consisting of the 4th and 5th squares of the c to f files), since it gives you ample space to mobilize your pieces and possibly launch an attack later on. On the other hand, ceding control of the centre gives you a cramped position that may be a pain to defend in the middlegame.
The two types of approaches which one may have towards the concept of centre control are the Classical and Hypermodern theories. In Classical theory, the idea is to control the centre by occupying it with pawns, before using pieces to support the pawn centre (hence the prevalence of opening moves like 1. e4 e5 and 1. d4 d5). This is also the most common idea that is taught to young beginners when they start learning chess.
On the other hand, Hypermodern theory states that control need not always be established through pawns in the centre; pieces can also use their long range abilities to control central squares from a distance. An even more counterintuitive method will be to allow the enemy to set up his pawn centre, before counterattacking it with your own pawns and pieces.
Because of the complexity of the Hypermodern theory, my advice to weaker players is to play safe and go with the Classical theory for now, and learn how to set up a strong pawn centre. Of course, if you do want a better understanding of Hypermodern theory and how to play such openings, then I will recommend you to the following link: http://nushsblackknights.blogspot.sg/2013/07/hypermordernism-and-kings-indian-part-1.html
4. Castle early, unless it is wrong to do so
Once again this doesn't need much elaboration; castling helps to keep the king safe and develop the rooks. While in rare instances it is indeed acceptable not to castle (see http://nushsblackknights.blogspot.sg/2013/10/the-right-time-to-castle.html for some examples of when it is actually better not to castle/delay castling), the best piece of advice will be to castle early in most positions.
To end off we will look at a sample miniature taken from Aaron Nimzowitsch's "My System". It emphasizes the importance of early development, and warns of the dangers that grabbing pawns too early in the opening (and thus lagging behind in tempo) may cause.
Nimzowitsch has helpfully provided ample annotations in his book, and I will include most of them over here.
Aaron Nimzowitsch vs Semion Alapin
Casual Game 1914
1. e4 e6
2. d4 d5
The French Defense: A simple example of exerting control over the centre (Point 3)
3. Nc3 Nf6
4. exd5 Nxd5
Nimzowitsch: "Surrender of the center"
5. Nf3 c5
Nimzowitsch: "To 'kill' the Pawn. 'Restraint' might have been effected by, say ...Be7, ...O-O, ...b6, ...Bb7."
Personally I don't like this move; while it looks aggressive, it also violates one of the fundamental points we went through just now: Don't push pawns unnecessarily unless it aids in development.
6. Nxd5 Qxd5
7. Be3 (D)
|Position after 7. Be3|
Developing and making threats at the same time helps to slow the opponent down. Here the threat is dxc5 winning a pawn.
Nimzowitsch: "Disappearance of tempo spells loss of time."
8. Nxd4 a6
9. Be2 Qxg2
Nimzowitsch: "Stealing a Pawn. The consequences are grievous."
10. Bf3 Qg6 (D)
|Position after 10. Qg6|
White is a pawn down, but he has developed most of his pieces. Black, in contrast, has only a mobilized Queen which is dancing around in the middle of nowhere (and violates the rule not to move a piece more than once in the opening!)
11. Qd2 e5
Nimzowitsch: "The crisis. Black means to be rid of the unpleasant Knight, so that he may in some measure catch up in development."
12. O-O-O! exd4
White has castled his king to safety and mobilized all his forces, while Black's pieces are still sleeping on the first rank and his king is stuck in the centre. Quite a good compensation for a pawn and a knight!
Nimzowitsch: "Travels by express. Any other Bishop move could have been answered by a development move, whereas now there is no time for this; Black must take."
14... gxf6 15. Bxc6+ bxc6 16. Qd8#
15. Rhe1+ (D)
|Position after 15. Rhe1+|
Nimzowitsch: "Play in the King and Queen files at the same time. The danger of a breakthrough is great."
Or 15... Be6 16. Qd7#
16. Bxc6+ Kf8 (D)
|White to move and mate in 2|
Or 16... bxc6 17. Qd8#
Now, try to solve the mate in 2 puzzle before scrolling down for the answer!
An elegant illustration of the fate of one who does not develop his pieces properly
So that was 4 basic but extremely useful tips for one to keep in mind, regardless of whatever opening line you choose. All the best!
"My System: 21st Century Edition" by Aaron Nimzowitsch