This one requires a big choice on your point. In The Elder Scrolls V: Skyrim, there's a civil war going on between the Imperials and the Stormcloaks (Skyrim natives). What it boils down to, is that you have to make a choice to join either the Imperials or the Stormcloaks, and help them advance their cause. Either way you go, you'll get the 'Taking Sides' achievement, which will get you 10G on Xbox 360, or a bronze trophy on PlayStation 3.
In this video by YouTuber pms00, check out a really great walkthrough on how to get the achievement. It's that easy!