1. Maximizing your piece activity,
2. Forcing the opponent's pieces to passive positions, and
3. Creating static weaknesses in your opponent's position.
The first principle is hopefully familiar to you. The importance of improving your pieces to the maximum is an idea that recurrs in many situations. It is also important to keep in mind that the opponent is trying to do exactly the same thing, so you should try to prevent the opponent from keeping his pieces in active positions. Finally, you should try to force a long-term weakness in the opponent's position. This usually means pawn structure, but sometimes it can be the bishop pair or a dominating minor piece. The following game illustrates these concepts:
The above game contained many key ideas. First, I played Nc5, trading off the knights. The trade in of itself did not accomplish much since the knights' positions were about equal, but the key is what is left on the board, and this trade activated my dark squared bishop. I continued with placing my queen on b6, activating it and also tying my opponent's rook down. I followed this with activating my rook and then playing f6 and e5, blocking out my opponent's active bishop. Patiently, I then activated my last piece, my light squared bishop, which allowed me to finally make serious gains on the queenside. My last critical move was Bd4, exchanging my dark squared bishop, which was doing little without the pawn on f2, for white's bishop which was contributing to the attack. This was enough to give me a large advantage, and ultimately I won the game. The most important thing to learn from this game was how I tirelessly improved my pieces. Often, the weaknesses and the action will come once you move all of your pieces towards their optimal positions.
Good Luck!
David Adelberg