Impossible Difficulty Combat Guide - XCOM WikiĬlassic/Ironman Mode Walkthrough. The best two threads I have come across are: There's a lot of good info and opinions out there, and some not so good of course. My first few runs taught me the game so I can do classic with DLC.
Like Nimrod said, it comes down to having a solid grasp of the game mechanics and planning ahead. My final run for the plat is going to be I/I