Get your pieces out into the centre quickly. The opening is a race to see who can get their pieces out first while keeping at least a share of control of the centre.
This is the main point to remember; all the other rules are just footnotes to this one. Sortez les pieces!
Get a firm foothold in the centre - a pawn on one of the 'little centre' squares e4/e5/d5/d4 - and don't give it up without good reason
Move your king to safety at the side by castling
Complete your development before moving a piece twice or starting an attack. By move 12, you should have connected your Rooks, or be about to do so.
More detail on winning the race:
move pieces not pawns, and
move them to their best squares in one move if you can, and also
try to gain time if you can by aggressive moves.
Move your minor pieces out early on generally move Knights before Bishops, and generally straightaway to f3/c3 or f6/c6 (but probably not both, as White)
Don't move out your major pieces (Q+RR) where they will get chased around by the little guys and possibly trapped.
Don't grab pawns or attack if you haven't completed developmen; especially, don't charge around with your Queen trying to hoover up pawns.
If one side gets ahead in development:
If you are ahead in development, start something going and open up lines for your better pieces
If you are behind in development, don't start anything and keep things closed until you have caught up. This is especially true if you have not castled!
Rooks are the hardest piece to develop: "openings should be judged on the prospects they offer to ambitious young Rooks" - PURDY. To develop your Rooks, open a file; to open a file, bring pawns into a position to swap them off; so after 1.e4, plan to play d2-d4 or f2-f4 soon.
In fact, you have to attack the opponent's centre with pawns to get much chance of an advantage as White (The Four Knights' Game is next to Old Stodge in drawishness), so d2-d4 makes sense for more than one reason.
Lasker's rules for the opening
Do not move any pawns in the opening of a game but the King and Queen pawns.
Do not move any piece twice in the opening, but put it at once on the right square.
Bring out your knights before developing your bishops, especially the Queen's Bishop.
Do not pin the adverse King Knight (ie. by Bg5) before your opponent has castled.
Reuben Fine on the opening:
In the initial position White, because of the extra move, has a slight advantage. Consequently:
White's problem in the opening is to secure the better position, while...
Black's problem is to secure equality.
Fine's rules for the opening
Open with either the e-pawn or the d-pawn.
Wherever possible, make a good developing move which threatens something or adds to the pressure on the centre.
Develop knights before bishops.
Pick the most suitable square for a piece and develop it there once and for all.
Make one or two pawn moves in the opening, not more.
Do not bring your queen out too early.
Castle as soon as possible, preferably on the king's side.
Play to get control of the centre.
Always try to maintain at least one pawn in the centre.
Do not sacrifice without a clear and adequate reason, eg.:
it secures a tangible advantage in development
it deflects the opponent's queen
it prevents the opponent from castling
it enables a strong attack to be developed
Fine's two last questions to be asked before a move is made:
How does it affect the centre?
How does it fit in with the development of my other pieces and pawns?
Nimzovitch's Seven Axioms
(from My System)
Development is to be understood as the strategic advance of the troops toward the frontier line (the line between the fourth and fifth ranks).
A pawn move must not in itself be regarded as a devloping move, but merely as an aid to development.
To be ahead in development is the ideal to be aimed for.
Exchange with resulting gain of tempo.
Liquidation, with consequent development or disembarrassment.
The pawn centre must be mobile.
There is no time for pawn hunting in the opening, except for centre pawns.
