Beaglerush [https://www.youtube.com/user/Beaglerush] does some very well thought-out LPs of XCOM: Enemy Unknown. His current series, Live and Impossible, is an uncut Ironman Impossible playthrough of the Long War mod for Enemy Within. The videos are really long as a result: the shortest is about half an hour, with the longest so far clocking in at three hours and seventeen minutes. However, you really can't ask for a better look at how to succeed in such a difficult game. He'll map out the level and explain his tactics throughout the missions, and it really shows in his success rate so far: by the middle of May, he's lost a mere five soldiers and the aliens are so resource-starved that Mutons haven't even appeared yet. He also will go through his choices for research, base management, equipment building and soldier loadouts.
The videos are very long for LP episodes, but they're well worth a look if you want to get into the fine details of how XCOM works at the Impossible difficulty level. Beagle's also a pretty animated guy, so it's pretty easy to get into the mood of the video and root for his soldiers as they get themselves out of some truly nightmarish situations.