Very easy to get in mission 4, “The Storm,” if you’re using stealth, as opposed to running and gunning. If you’re taking it slow and using stealth with Iden, you’ll come to a spot outside, about mid-way through the ground component, where a Scout Trooper has his back to you. You really can't miss it. Wait for the patrol to pass and then cross the road to take out the Scout with the stealth takedown (right stick). Enjoy your 30gs.
Game smart, not hard.