Press ~ during game play to display the consolewindow. Then, enter one of the following codes to activate thecorresponding cheat function.
Enter these whilst on the console.
Play on five maps other than the standard ones or ones from Valve and have at least one kill. Enlisting the help of a friend will make this easier.
Enlist the help of a friend and kill him with both of you using melee.
Set the system date to December 25, 2011. Multi-player mode is not required. Load a map, spawn some bots, and about every third one will drop a gift.
ntgo wtlu auvwyrgwytir uvlec
Enlist the help of a friend. Kill him and pick up his weapon. Have your friend enable the retry code and join again. Have him select another model. Kill him again and pick up another weapon. If he throws the grenade, pick up it and throw it back. Repeat the process as many times as needed.
There are a total of 52 achievements. These achievements can be viewed in steam under: Community -> View all [No. of games] games -> View Stats (Under Day of Defeat: Source)