Opening Principles
In a match of chess there are usually 3 parts, the opening when you develop your pieces, the middle game when you start trading and winning material, and the endgame when there are little to no pieces and just pawns. The opening will likely determine a large part of the game. You need to follow a few principles in the opening.
1. Control the center
2. Develop towards the center
3. Castle early
4. Knights before Bishops
5. Develop all your pieces
6. Don't bring out the queen too early
7. Don't move the same piece more than once in the opening
If you follow those principles your opening will be good. That's why you see grandmasters play games like this:
And not like this:
In the first game each piece that was developed was attacking the center. In the second white was lucky that the opponent didn't see the checkmate. You should always try controlling the center because your pieces can do the most in the center. This is also the reason you develop towards the center and not the flank (side).
You should castle early usually because that's where your king is most safe. Only when there are pawns and a few pieces should your king come out.
You should always develop knights before bishops because bishops are more dynamic than a knight. A knight has 1 optimal square usually, c3(for b1 Knight) f3( for g1 knight), and reverse for black knights. A bishop can be used to block a pin, or pin something itself. Or maybe it wants to Fianchetto to take control of the long diagonal.
You should always develop your pieces because you want an empty back rank(except for a king and maybe the rooks) because if you do all your pieces are in the action and you'll dominate.
You shouldn't bring your queen out because it's going to get harassed by every piece and be forced to move, wasting time(tempi) you could be using to develop your pieces.
