For this achievement you need to play a match on each of the 7 new maps from the Dark Corners DLC.
Here's a list of the 7 maps you need to play a game on for the achievement, use it to keep track of which maps you play on;
• Allfathers Garden
• War Machine
• Way Station
Now the achievement is left entirely open as this can be obtained by playing a match in any mode, so while you have the option of playing online in a ranked/social match and working toward this achievement casually you can also choose to get this achievement out the way by playing a local game with 2 controllers.
The quickest way to get this achievement is to set up a local game, set the game type to Warzone, set the round limit to 1 and work your way through the maps while killing the second player, this way you have absolutely no threat to contend with as the second player won't do anything unless you make it.
You can use this method any way that you want, you can set up a match with you facing off against a team of bots if you want, it's entirely up to you, I've just outlined the easiest and fastest method that I know of.
Using this method will also net you; Did Not Go Gentle in Gears of War 2
at the same time, that achievement requires you to win on each of these maps.