Often, you memorize a specific opening line ten or more moves deep from either experience or study (i.e., I know Evans Gambit to about fifteen moves and Sicilian Najdorf to even more in some cases).  But then, your opponent deviates from the main line on the first move!  What do you do then??

Well, after your opponent makes a questionable move, you must first identify why that move isn't book.  There are always reasons that your opponent's moves aren't book.  Generally, you need to develop quickly and place your pieces aggressively.  Most importantly, you must always look for tactics!!

So, I have found three games in which I play against an odd move or two, and I use those mishaps to my advantage.

1. In this game, my opponent declines my sharp, tactical center game in order to develop his queen...  Generally not a bad idea.  This game also shows the importance of playing with a good plan.

2.  This time, my opponent plays a few acceptable variations of the Sicilian, but his odd combination of them leads to disaster on all parts of the board.

3. This game, another Sicilian, features a few premature moves that are okay, but require preparatory or supplementary moves, which are not played.  It is quite exciting and full of tactics!

I hope these examples have helped enlighten you!  Just to recap, the few things you must do are:

1. Determine why the move is not a book move.

2. Devise a plan, and find any tactics.

3. Develop quickly, and place your pieces aggressively!

Now, go punish your next opponent in the opening!