The Low Road
Find the nearest camera and hack to profile your target. Use ctOS scan to mark all enemies in the area; otherwise, manually tag them using the security cameras nearby. Like before, you can snipe the guards from a distance; just be prepared to use a Jam Coms if ever a civilian calls 911. Once you've cleaned the area, take down the target to complete the mission.
The Tower
Head to the parking building where the target is hanging out. You have to engage the guards here at close range so if you have silenced weapons, this is the best time to use them. Use the cameras to find and profile the target. Tag enemies using the camera or just use a ctOS Scan item. Take note that if the target is alerted, he may try to escape; it will make the mission go longer so a silent approach is fast and efficient in getting things done.