How to Get the 'Overachiever' Achievement in Modern Warfare 3

Modern Warfare 3's Spec-Ops mode is what's keeping me coming back every other day, and I'd imagine that's the same situation for everyone that owns the game. Today, the Achievement Hunters are going for all 48 stars in the Spec-Ops missions. This is pretty tough, because you have to play on the hardest difficulty. Because I'm a sissy-man, I can only imagine that it'll take me a long time to complete this one.

• Xbox 360: 40G
• PlayStation 3: Silver trophy