Serial Cleaners

Nice and simple. Just take your sweet time when moving about. Crouch when necessary, or hide. You play the game on easy, and you'll have a far more lenient time with this one. Just complete the objectives as normal, and learn to track where the officers patrol. I got this on my first mission after the intro. Obviously, getting this out the way on an earlier mission is advisable. Just restart the mission if you get busted.