Opening preparation : analysing your own games
Analysing your own games is a must to improve in chess. That's obvious. One easy way to improve is in opening lines, by just looking up the most common moves with an opening database.
Here's 3 games against the same opponent in which I was surprised by a move that I didn't know.
After the first game I did not do my homework, since I thought my play was okay. After the second game, I did do my homework and found out that the surprise move by my opponent was just plain bad !
And here the 3rd game in which I "finally" had done my homework :