People should analyse their games in order to improve at chess. But how should they go about this? First and foremost you must have good record of your game. What I mean by a good record is that you should write down ideas behind each move shortly after finishing the game.
Blunder checks and tactical oversights are best done with a computer program, which can help a lot. Once you know what you have missed tactically what else can you do? Here I have an idea. Categorize your games according to opening and generate tactical puzzles using your games. This can be done with Fritz. Soon you will notice any pattern of error in a particular opening and practicing those puzzles repeatedly will help you much more than solving tactical puzzles from a book.
Levers: Master play is based on pawn structure so it is wise to analyse which pawn levers you and your opponent missed in the relation of piece placement and time. I think this is essential in developing middle game play and positional play.
Compare your ideas with those of a stronger player or coach. For example you prefer to play Rfe8 in order to bring rook into action but your coach want you to play Rfe8 in order to bring Nf6-d7-f8 to protect your king. The moves are the same but with different reasoning behind them. This will help you understand the position better and the logic behind the move played.