If you use Trevor to start the mission, the mission waypoint will be at the L.S. Police station. When the mission begins, enter the L.S.P.D. and make your way to the rooftop via the Locker Room doors.
Take the stairs to the roof and enter the helicopter to begin scanning some perps!
If you decide to do this mission as Franklin, the mission waypoint will be at the FIB lot in El Burro Heights. Approach the waypoint and the game will shift to Trevor arriving by helicopter. From here, you are required to switch to Trevor to continue the mission.
The blue-colored arrows indicate which direction to move the camera, so steer the camera towards Franklin's location and then scan him. When that's done, move the camera towards the next set of blue-colored arrows to find some more individuals to scan.
GOLD MEDAL REQUIREMENTS: "EAVESDROPPER
Most of these people have some interesting things to listen in on, but you don't need to hear all of it. After a few seconds of listening, SCAN the individual and then move to the next person and scan them. Scan three conversations for the Gold.
After scanning the first set of people, the helicopter moves towards another section of town. The person that Trevor needs to find is all the way on the lower left side, so scan him to make the positive ID on Chad Mulligan.
From there, keep your eye on Chad as he walks through the streets and then eventually gets in his car and drives off. Keep the camera focused on Chad as he drives erratically thru the streets so that Franklin can follow. After several twists and turns, Chad enters a parking garage and disappears.
GOLD MEDAL REQUIREMENTS: "I SEE YOU
When prompted, move the camera all the way to the LEFT side to see Chad sitting in his car (if you scan him, he'll be cursing to himself).
Once Chad has been ID'ed, it switches over to Franklin. Equip a Stun Gun and blast a bolt into Chad (or leave him be). From there, enter the Z-Type and drive to LS Airport.
GOLD MEDAL REQUIREMENTS: "NOT A SCRATCH
Park the car at the airport to trigger a cutscene with Devon. When that's done, take one of the cars in the hangar and drive outta the airport to complete the mission!