Every Modern Warfare game has had bits of enemy intel for you to recover, and they're always hidden within the level. The few pieces I've uncovered across the series has always been through dumb luck. But if you want that 'Scout Leader' achievement, you'll have to find all 46 pieces of intel throughout the entire single player campaign.
Good luck with this one. In my first run through the game, I think I was able to find...eight pieces of intel. It's a good thing videos like the one below exist. NextGenWalkthroughs has a lengthy, but incredibly detailed walkthrough in which they find all 46 pieces of intel.
- Xbox 360: 35G
- PlayStation 3: Silver trophy