Beginner:
Control of the center, you should have pieces attack the center squares to put stress on the opponent. Simply put, pieces are less likely to attack on the outside of the board because they the pieces will have less options to move and attack. When you take control of the center it removes the ability for the opponent to use them to their ability.
Intermediate:
Pawns can be used as a great tool. These little guys, although weak, can be a powerful force in a long game. Pushing pawns and giving them the tender loving care they need helps put pressure on the opponent while advancing the placement of your pieces. Next game try using pawns as a tool instead of a stale wall or suicide piece.
Advanced:
Bad bishops are bishops that you do not properly utilize. For example: When you attack an opponent from the left side of the board you cannot utilize the mobility of the piece in all directions. You cannot attack top left, or bottom left. You should also move your pawns so they are not in the way of your bishop. Around mid game to late game this is important. If you have a white square bishop you should move your pawns to the black squares and visa versa if you have a black bishop.
