As mentioned in the previous post we are going to need a large database of chess games.
Where can be found such a database? I’ll mention some possibilities in this post.

Downloading by means of ChessDB
Within the Tools menu of ChessDB a “Download Games from …” option is offered to download a database of 100,000 games in the Elo range 2290 to 2851 or a huge database of over 3.5 million games. In addition ChessDB offers a possibility to update this database by downloading games from TWIC and importing them into the database.

TWIC
Each week The Week in Chess (TWIC) publishes a new zip file with PGN files of recent games. As mentioned above ChessDB has some functionality to download the recent chess games from The Week In Chess website, but you can also download the games by yourself (for example when using another database program).
MillBase contains the complete set of games.

ICOfY
Another free large database can be found at ICOfY. This large database contains more than 5 million games.

Chessopolis
If you are more interested in a specific opening the downloadable game collections at Chessopolis may be a nice place to start looking. Here you can find the Game collections by opening.