Easy achievement. All it requires you to do is "play" for 20 hours, but leaving your xbox on counts as playing. If you play this game for any other achievements, you should already have a couple hours put in, and if you're planning on finishing any other achievements I'd recommend not trying to 'boost' this achievement until you're done with the game. If you don't have it by then, all you have to do is leave your xbox running in your crib with your controller plugged in to avoid it disconnecting.
20G and 31TA points are yours :)