"Move every piece once before you move any piece twice, unless there is a tactic" is the grandaddy of all opening principles. But it's certainly not the only thing you need to know about openings (to say the least). One piece of opening knowledge that turns out to be very helpful is to understand the generalities of the two main opening philosophies, Classical and Hypermodern. There is no official chess dictionary, so what I am about to show you is my understanding of Classical Development (so it won't make sense to write "But Tarrasch said...!").
One reason this is helpful is that if your opponent makes a move where you don't know what to do (or if the opponent's move basically does nothing at all), sometimes it is helpful to ask "What would Classical (or Hypermodern) Development suggest I do next?" or "When would Classical Development suggest I develop my queen's bishop?", etc. The opponent, of course, is not only going for similar aims, but will often do things to prevent your pieces from getting so powerful. That's one of the fun things about chess, but first things first: let's just start by assuming the opponent is not moving at all, so you can at least get the idea of what you are "ideally" trying to achieve.
Classical development consists of a bunch of steps that enable you to activate all your pieces (read this as non-pawns), emphasizing occupation (as opposed the Hypermodern's "control") of the center.
One reason why Classicists preferred occupation is because it implied both superior mobility and flexibility. For example, a knight in the center of an empty board has 8 possible squares to move; a knight in a corner only has 2. Moreover a knight in the center can get to any (random) part of the board much more quickly than a knight that is not centralized (obviously it can get to the area it already stands most quickly).
Here are my steps of Classical Development. Each move assumes certain basics like the move is safe and the best squares very much depend on what the opponent has done. Then, after all the steps, I will give an example diagram of each (it's easier that way for blogs...):
1. Move out a central pawn (d or e-pawn) two squares.
2. If the opponent does not make it inconvenient, move the other central pawn two squares so that now you have e4/d4
3. Move out the knight on the side you are going to castle toward the center.
4. Activate the bishop on the side you are going to castle.
5. Assuming you are going to castle kingside, Castle kingside. If you are going to castle queenside, move the queen out a little to a safe square so you can castle next move. The following steps will assume you castled kingside.
6. Move the knight out on the opposite side, preferably toward the center and preferably not blocking the bishop.
7. Move the bishop out on the opposite side to an active square.
8. Move your queen up a little to connect the rooks.
9. Activate one of your rooks
10. Activate the other rook.